TECH LIBRARY 1 SVPP Supplier Manuals Everight Alliance S1AmanualRev022610V13.pdf

ELECTRONICS

SUPPORT

SENSOR

Signal Conditioner for AC LVDTs, RVDTs, LVRTs, and Half-bridges

Set-up and Operating Instructions

Everight Sensors Corporation 102 Commerce Drive, Unit 8 Moorestown, NJ 08057 USA www.everightsensors.com

Rev 2-1-10 http://www.everightsensors.com/

PREFACE

In this manual, you will find a chart on page 4 for connecting your AC-LVDT, RVDT, LVRT, or inductive half-bridge sensor quickly to this model S1A DIN-rail mounting, 24 Volt DC-operated signal conditioning module and a Quick Start Guide on page 5 for calibrating it with two front-panel push buttons, eliminating any need for pot adjustments with a screwdriver. The specially developed software functioning within the internal DSP (Digital Signal Processor) will lead you through the various calibration steps by means of the three green LEDs on the module’s front panel, as illustrated on page

2. Note that the term LVDT is used generically throughout the instructions for audio frequency AC-voltage-operated position sensors, i.e. LVDTs, RVDTs, LVRTs, and inductive half-bridges.

You will also find the S1A specifications and a more detailed description of the functions available for applications where you may wish to go beyond the basic features. Such possibilities include the master/slave synchronization of the LVDT excitation, the open-collector failure warning flag output, the null position indicator signal, and digital communications via the RS-485 addressable multi-drop port.

The S1A LVDT Signal Conditioner is both RoHS and compliant. To assure a long, maintenance-free life, all inputs and outputs are equipped with ESD protection, as well as protections against reverse voltage, overvoltage, and short circuits. Operating current and power-on inrush current are also limited by solid-state resetable fuses.

TABLE of CONTENTS Identification of Front Panel LEDs and Switch Functions 2 Identification of DIP Switches and I/O connections 3 LVDT Wiring Configurations 4 Quick Start Guide 5 Functional Description 6 DC Power Input` 6 LVDT Primary Excitation 6 AC Half-Bridge Connections 6 Master/Slave Synchronization 6 LVDT Output Signal 7 DC Output Filtering 7 Failure and Fault Indicators 7 RS-485 Communications 7 Expanded Calibration Procedure 8 Terminology and Definitions 8 Calibration Procedure 8 Null Point Location 8 Null Indicator Output 9 Setting Full Scale Output Point 9 Setting Zero Output Point 9 Live Zero and Extra-range Outputs 10 Using the Voltage and Current Outputs 10 Failure Diagnostics 10 Failure Warning Flag 11 Failure Warning by Out-of-Range Output 11 Alternative Calibration Procedure 11 Troubleshooting LVDT Connections 12 Grounding and Shielding 12 Commands for the RS-485 Port 12 Specifications and Module Dimensions 13 EC Declaration of Conformity 14 Product Warranty 14

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Identification of Front Panel LEDs and Switch Functions

(Use with Quick Start Guide on page 5)

RUN Mode

Flashing = Failure

Model Identification (S1 or S1A)

CALIBRATION Mode

Dome switch for setting Full Scale in CALIBRATION mode

LEDs indicate calibration steps, Null point, and LVDT failures

Adjacent LED indicates core is above Null point core is around Null point core is below Null point

Dome switch for setting Zero in CALIBRATION mode

Adjacent LED flashes if LVDT Primary is open

LVDT Excitation fails

LVDT Secondary is open

Figure 1.

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Identification of the pc board-mounted DIP switch functions & I/O connections

(Use with Quick Start Guide on page 5)

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DS1 Position 1 2 3 4 Output with DS1-No. ON

0 to 5 Volts

1 to 5 Volts

0.5 to 4.5 Volts

0 to 10 Volts

J1-1 Black LVDT Primary H J1-2 Black LVDT Primary L J1-3 Black LVDT Seconda J1-4 Black LVDT Seconda

J2-1 Blue LVDT "Center T J2-2 Blue Failure Flag (O J2-3 Blue -15 V DC input J2-4 Blue Sync Input / Ou

J3-1 Green RS-485 (Digital J3-2 Green RS-485 (Digital J3-3 Green Analog Output J3-4 Green Analog Output

J4-1 Red Null Indicator D J4-2 Red Null Indicator D J4-3 Red Power Return ( J4-4 Red Power Input (+)

DS2-1 and DS2-2 Switch positions

Excitation Frequency

DS2-1 & DS2-2 both OFF 1 kHz DS2-1 ON & DS2-2 OFF 3 kHz DS2-1 OFF & DS2-2 ON 5 kHz

DS2-1 & DS2-2 both ON 10 kHz

DS2

1 2 3 4 5 6 7 8 J1

J2

DS1

J3

J4 1 2 3 4 5 6 7 8

J 7 DIP switch factory settings:

3 kHz excitation frequency, 0 to 10 Volts DC output.

J7set for 3.0 Vrms drive

Figure 2 Internal DIP Switch Locations

Table 1. Excitation Frequency Settings 5 6 7 8 -10 to +10 Volts

0.5 to 9.5 Volts

0 to 20 mA

4 to 20 mA

DS2 - 3 4 5 6 7 8

Switch

ON

Invert Output

Hz add add add add

Table 2. S1A Analog Output Settings Table 1a. Special Outputs and Unit Address igh or Half-bridge High ow or Half-bridge Low ry Low (Common Ground) ry High or Half-bridge Mid-tap ap" Junction Point (No internal connection) pen Collector, +24 V DC, 50 mA max.)

for ±10 V DC output or Common Ground (J8 in) tput (Master / Slave Bus)

Data Line B) Data Line A) (-) (Common Ground) (+) (Voltage or Current, as selected by DS1) ifferential DC Output (floating) ifferential DC Output (floating) -) (Common Ground) (+15 to +32 V DC) Figure 3.

Front View Table 3. S1A LVDT Signal Conditioner module I/O connections

a) 3-Wire LVDTs/RVDTs (see note 4) b) 4-Wire LVDTs/RVDTs

c) 5-Wire LVDTs/RVDTs d) 6-Wire LVDTs/RVDTs (see note 5)

e) Half-Bridges and GE LVRTs

Notes:

1. J1-1 through J1-4 and J2-1 are connections to signal conditioner’s screw terminal plugs.

2. LVDT/RVDT secondary windings are shown connected in series-opposition, where ● indicates windings’ magnetic polarization.

3. Letters in parentheses are connector pinouts for typical

5- and 6-wire LVDTs or RVDTs and for GE half-bridge-style LVRTs.

4. A 3-wire LVDT/RVDT connection applies only ½ nominal excitation voltage to primary.

5. 6-wire LVDTs or RVDTs require secondaries be connected externally in series-opposition, preferably as close to the sensor as practical.

r Figure 4. LVDT and Half-Bridge (LVRT) Wiring Hook-Ups To S1A Signal Conditione

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Quick Start Guide

1. If you are able to utilize the factory default settings for DC output and excitation frequency, skip to Step 3. Otherwise, open the S1A module’s case by pushing the locking tab inward on both of the thin sides and sliding the case rearward to expose the two circuit-board-mounted DIP switches.

2. Set the pcb-mounted DIP switches: The factory set LVDT excitation frequency is 3 kHz, which is suitable for most LVDTs, but it can be changed by setting DS2-1 and DS2-2 according to Table 1. The DC output is factory set at 0 to 10 V DC, but it can be changed by setting DS1 (indicated as OUT on the pc board) according to Table 2. When DIP switch changes, if any, are finished, slide the pc board back into the case on its tracks and snap the two sections of the module’s case together.

3. Mount the module: Remove the color-coded plugs from the S1A module and install the module on the DIN rail by hooking the bottom of the module’s rear edge under the bottom edge of the rail, and then pressing the module back against the rail until the module's spring-loaded rail catch engages the top edge of the rail. To remove the module from the DIN rail, insert a flat-bladed screwdriver into the slot in the metal catch at the back of the module, lift the catch, and disengage the module from the rail.

4. Make the I/O connections: Following Table 3 and the schematics on page 4, use the color-coded screw-terminal plugs to connect the LVDT primary and secondaries (and the “center tap pair” junction point if needed), DC power, and the analog output to the system or indicator, as set in Step 2. When finished, insert the colored plugs completely back into the corresponding colored jacks on the module.

5. Calibrate the LVDT’s core positions: When the appropriate DC power is applied, the red POWER LED should glow steadily and the green LEDs should be off. If any of the 3 green LEDs are flashing, check the LVDT connections: P indicates open primary; S indicates open secondary; E indicates loss of excitation. If the S or E LED is illuminated or flashing, check the set up to clear any errors. When only the red POWER LED is on, the calibration procedure can be started. Note: The LVDT’s core must not protrude from the LVDT at any point during the calibration process or erroneous calibration will result.

► Shift the module into CALIBRATION mode by depressing both the FULL SCALE and ZERO buttons simultaneously for about 3 seconds, until the red POWER LED flashes. The module is now functioning in the CALIBRATION mode

► One of the green LEDs will be illuminated, indicating that the LVDT’s core is on one side or the other of null, or at null. As the LVDT’s core is moved inward, that LED will go out and the middle LED will come on (showing the LVDT is at Null), then the middle LED will go out and the LED on the opposite end (compared to the first green LED that was on) will come on. Adjust the LVDT core’s position until the middle green LED is on. The LVDT’s core is now approximately at its Null position.

► Set the workpiece whose position is being measured so that it is located at the middle of its range of motion when the LVDT’s core is at its null position. Mechanically couple the LVDT core to the workpiece in this position. Move the workpiece (now coupled to the LVDT’s core) to the Full Scale (maximum travel) position. Depress the FULL SCALE button until the green LEDs flash once.

► Next, move the workpiece (now coupled to the LVDT’s core) to the Zero (start of travel) position at the other end of its range of motion. Now depress the ZERO button until the green LEDs flash once.

► If one (or both) of the green LEDs is still flashing, rerun the calibration procedure by moving the workpiece and the coupled core to the end position indicated by the flashing LED and depressing its nearby button. The red LED should be flashing, showing that the module is in CALIBRATION mode. To return to RUN mode, depress both the FULL SCALE and the ZERO buttons simultaneously for about 3 seconds until the green LEDs go out and the red POWER LED turns on steady. Verify that the analog output and its direction (slope) is that which was desired. If the output is reversed, switch DS2-3 to on.

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Functional Description of the S1A LVDT Signal Conditioner

The S1A LVDT Signal Conditioner is an intelligent module which uses a DSP (digital signal processor) chip to sequence and control the various functions of the module. The following descriptions are provided to assist the user in setting up and applying this module.

DC Power Input The input power range of 15 to 32 V DC covers the common +24 V DC industrial power supply and the older +15 V DC. If the input voltage is above 32 V, a Zener diode will conduct, and a PTC resetable fuse will open if the current becomes too high. After cooling, the fuse will reclose to allow normal functioning to resume. The S1A module avoids a high inrush current with an NTC current limiting device in series with the power circuitry. The module’s input is also protected against reverse polarity connection and ESD. For ±10 Volt output, +15 V DC is input to J4-4 and -15 V DC is connected to J2-3.

LVDT Primary Excitation The AC-LVDT’s primary is excited by a digitally synthesized low distortion (≤1% THD) sine wave signal.

The nominal excitation frequency selections are 1, 3, 5, or 10 kHz. The sine wave synthesizer operates from a crystal oscillator, so the resulting frequencies will be very stable. 3 kHz is chosen as the factory default setting, since most commercial LVDTs specify 2500 to 3300 Hz excitation and will operate very satisfactorily at this frequency. To select another of the excitation frequencies, it is necessary to open the S1A module’s case and change the setting of DIP switches DS2-1 and DS2-2 according to Table 1.

The amplitude of the excitation sine wave is very stable because of the digital synthesis process. The excitation driver operates in push-pull mode to provide about 3 Volts ACrms to the LVDT’s primary, but for unusual cases, the drive voltage can be increased by 50% by removing internal jumper J7, or decreased by 50% by exciting the primary single ended to ground (J1-1 to J1-3). A fault detector in the LVDT’s excitation circuitry detects if the LVDT’s primary is electrically open-circuited or disconnected. If so, the green P LED on the front panel flashes and the failure warning flag output at J2-2 is triggered

Inductive Half-Bridge Connections An AC inductive half-bridge sensor or LVRT is similar to an LVDT, but combines an LVDT's primary winding with a center-tapped secondary winding. AC excitation is applied to the ends of the winding and the output signal is taken from the mid-tap. To hook up a half-bridge or LVRT sensor to the S1A signal conditioner, connect the high end of the half-bridge winding to terminal J1-1, the low end of the winding to terminal J1-2, and the mid-tap to terminal J1-4. The module will function the same as it does for an LVDT and will demonstrate the same fault indications as for a failure of the windings of an LVDT.

Master/Slave Synchronization When multiple LVDTs and their interconnecting wiring operate in close proximity, beat frequencies or heterodyning could occur if slight differences exist in the excitation frequencies of the modules. If a beat frequency develops, it will be observed as very low frequency amplitude modulation of the modules' DC output. The best way to avoid such interaction is to synchronize each module's excitation to exactly the same frequency so that beating cannot occur. Typically, one module is chosen as master and the other modules are slaves connected synchronously to the master, using the built-in auto-master sync system.

The modules' syncing can be implemented as follows: First, all modules must have their excitation DIP switches DS2-1 and DS2-2 set for the same nominal excitation frequency. Second, each module must have a different unit address, which can be set from 00 through 15 by DIP switches DS2-5, DS2-6, DS2-7, and DS2-8 in accordance with Table 1a on page 3. No duplicate addresses are allowed. The factory default address, 00, is usually applied to the master module. Finally, terminal J2-4 of the master module is connected to terminal J2-4 of up to fifteen slave modules. All the sync connections are protected against ESD or erroneous connections. If the master oscillator fails, a new master will be automatically developed to control the excitation oscillator frequency, thereby providing true fail/safe operation. If all of the modules are not powered up at the same time, the module with the lowest numerical address at initial power up becomes the master, as indicated by the P LED being steady on.

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LVDT Output Signal The two secondaries of the LVDT are connected together in series-opposing to develop a differential signal. This LVDT output circuit also has a built-in fault detector to warn if the secondaries are open-circuited, not connected together, or the cable is disconnected. Any fault or wiring failure flashes the green S LED on the module’s front panel and triggers the failure warning flag output at J2-2.

The differential signal from the LVDT’s secondaries is demodulated, buffered, and then sent to a 13-bit analog-to-digital converter (A/D) built into the DSP. The amplitude of full scale LVDT output signals accepted extends from 50 mVrms to 5 Vrms, a 40 dB dynamic range. The DSP scales the digital data as needed for the output type that is selected. The digital data are converted back to an analog signal by a digital-to-analog converter (DAC). This analog signal is passed to a buffer/driver stage from which the signal is then delivered as one of the eight user-selectable analog DC outputs: 0 to 5 V, 1 to 5 V,

0.5 to 4.5 V, 0 to 10 V, -10 to +10 V, 0.5 to 9.5 V, 0 to 20 mA, and 4 to 20 mA. All unipolar analog outputs feature a “live” zero, whereby the output can go below zero, so a user can establish a true zero.

The analog output is selected by setting one position of 8-section DIP switch DS-1 inside the module to on, in accordance with Table 2. The factory default analog output is 0 to 10 Volts (DS1-4 on). Besides selecting a specific analog output signal using DS-1, a user can invert the output signal by setting DIP switch DS2-3 to on, effectively reversing the slope of the output signal. For example, inverting the 4-to- 20 mA output changes it to 20-to-4 mA over exactly the same range of motion for the LVDT’s core.

DC Output Filtering Within the DSP, the digitized demodulated LVDT signal goes through some digital filtering before being input to the DAC. Its analog output is first sent to a single-pole low pass R-C filter having a -3 dB cutoff frequency of approximately 10% of the excitation frequency set by DS2-1 and DS2-2, and then to the output terminals. For applications requiring very low noise and ripple, the analog output can be subjected to further filtering by turning DIP switch DS2-4 on, which engages a single-pole low pass filter with a -3 dB cutoff frequency of about 10 Hz. The factory default setting for DS2-4 is off.

Failure and Fault Indicators The green front panel LEDs will flash to indicate failures in the cases of an open LVDT primary (P), an open LVDT secondary (S) or loss of excitation (E). The DSP determines a loss-of-excitation condition exists if anything causes the digital signal to the sine wave synthesizer to be lost. Any of these faults will trigger the failure warning flag, which is an open-collector-type output that pulls the failure warning flag terminal (J2-2) to common ground (J4-3) for any case where the DSP detects a fault or failure. The failure warning flag terminal includes protections against overcurrent, overvoltage, and ESD. Page 10 and Table 6 offer more detailed explanations of the LED indications and the failure warning flag output.

RS-485 Communications The S1A incorporates a two-wire RS-485 communications multi-drop interface for up to16 devices. The RS-485 communications permits a module to be set up and calibrated remotely and various data to be read or stored at a PC or terminal. A PC utilizing an RS-485 serial port converter can be connected as a data terminal to module terminals J3-1 and J3-2 to implement specific commands listed later in this manual on page 11. Any command sent to the module must start with the letter "U" followed by the module’s specific address identification number, which can be set from 00 through 15 by DIP switches DS2-5, DS2-6, DS2-7, and DS2-8 in accord with Table 1a. The factory default address setting is 00.

A Graphic User Interface (GUI) program that communicates via the RS-485 multi-drop com link with an S1A is being made available for download from the following website: www.everightsensors.com. The GUI facilitates setting up, calibrating, and monitoring any S1A on the multi-drop network from a remote computer or terminal. It also facilitates saving system-specific configuration data in files which could be reloaded into another S1A module. If all the S1A signal conditioners for a particular application (up to

16) were connected in an RS-485 multi-drop configuration, that network could be connected to the internet or to a wireless interface with the appropriate third party hardware and software, which would permit remote calibration or configuration at a location distant from the modules themselves.

http://www.everightsensors.com/

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Expanded Version of the Calibration Procedure

Terminology and Definitions To provide a clear explanation of the operation of this product, it is necessary to properly define the following words: program, setup, and calibration. To understand this manual and module, the word program is used to describe the operating system resident within the DSP, which is factory loaded and is not accessible to the user. The word setup is used to describe the settings chosen by the factory or the user for the LVDT’s excitation frequency, analog DC output, and other parameters that can be selected either by the internal DIP switches or via commands using the RS-485 communications port.

Setup should be done in accordance with the Quick Start Guide and the DIP switch settings on page

3. Besides switches for excitation frequency and analog output, there are choices for extra low pass filtering to improve signal-to-noise ratio, inversion of output slope, and up to 16 RS-485 addresses.

The word calibration is used to describe a process or sequence of actions by which the range of motion of the workpiece is matched to the range of motion of the LVDT to produce the desired system output.

First, the LVDT’s body is clamped in place. Next the LVDT’s core is moved to find its Null point or mid-range position. The LVDT’s null point is the only repeatable unique position of the core; there is no definable full scale or zero position for most LVDTs. The workpiece is set for the middle of its expected range of motion and then the LVDT’s core is mechanically connected to it. The LVDT core and connected workpiece are moved to their Full Scale or final position so the module’s Full Scale Output can be set accordingly. Finally, the LVDT core and connected workpiece are moved to their Zero or starting position, where the module’s Zero Output can be set, completing a typical end-point calibration procedure for the LVDT-based position measuring system.

Calibration Procedure On the front panel, there are three green LEDs positioned vertically and a red LED for power indication.

The power LED normally glows steadily when power is applied and the signal conditioner is in its RUN mode. When the module is in its RUN mode (not in CALIBRATION mode), the green LEDs flash only to indicate failures and, in master/slave operation, the P LED will glow steadily on the master module.

When in CALIBRATION mode, the green LEDs indicate the position of the LVDT’s core in relation to its null point. To enter CALIBRATION mode, depress the FULL SCALE and ZERO buttons simultaneously until the red LED flashes, indicating the signal conditioner is in CALIBRATION mode. The module can also be put into CALIBRATION mode by sending the appropriate command via the RS-485 port. (See page 11 for a listing of the RS-485 commands).

Null Point Location After entering CALIBRATION mode from RUN mode, as described above, it is possible to find the LVDT’s null point by moving the core and watching the green LEDs. In CALIBRATION mode, the three green LEDs operate according to Table 4 below as followings: if the core is far into LVDT’s positive side (above null), only the uppermost (+) LED will glow. This means the core should be moved in the direction expected to be toward null. As the core approaches the null point, the center (0) LED will light (at null). If the movement of the core is continued (below null) in the same direction, then the bottom (-) LED will glow. In this way, an LVDT’s core can be positioned sufficiently close to the LVDT sensor's mid-range position for reasonably accurate calibration. Note: The LVDT’s core must not protrude from the LVDT during any null point measurement or else false null indications can result.

Above Null

At Null

Below Null

Table 4. Finding an LVDT’s null in CALIBRATION mode: LED state vs. LVDT core position

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Null Indicator Output During CALIBRATION, the green front panel LEDs are used to show the position of the LVDT’s core in relation to its Null point. To find the Null point with better resolution, or for a continuous Null indication, connect an ungrounded DC voltmeter between terminals J4-1 and J4-2, the Null Indicator output. With the LVDT’s core at Null, each terminal is floating at about 1.5 V DC with respect to common ground, so the voltmeter will read zero volts between the terminals. As the LVDT’s core is moved, one terminal’s voltage increases toward +3 V as the other terminal’s voltage decreases toward 0 V (and vice versa for the other core direction), for a maximum voltmeter reading of about ± 3 Volts DC. The LVDT’s core must not protrude from the LVDT during any null point measurement or false null readings can result.

Setting the Full Scale Output Point Once the LVDT core’s Null position has been found and the core has been mechanically connected to the object whose motion is being measured, the next step is to calibrate the Full Scale output of the measuring system. This step assumes that the range of motion will be symmetrical with respect to the LVDT’s null point, but the process works for asymmetrical measuring ranges as well, as long as the Full Scale and Zero points are not on the same side of null. This step also assumes that the desired Full Scale output was selected either by accepting the factory default of 0-to-10 Volts DC or by setting DIP switch DS1 during the initial setup for another analog output based on the switch settings of Table 2.

The red POWER LED should still be flashing, indicating CALIBRATION mode. The core with its attached workpiece must be moved to the desired Full Scale (maximum travel) position. Once the core is in the Full Scale position, depress the FULL SCALE button on the front panel until the upper green LED flashes once. Alternatively, a digital command can be sent via the RS-485 port. The LED flash indicates that the Full Scale position calibration has been accepted. If an error occurred and it is desired to set the Full Scale again, depress the FULL SCALE button again and the Full Scale calibration will be updated with this new position as indicated by another flash of the upper green LED.

Setting the Zero Output Point When Full Scale calibration is complete, the core with its attached workpiece should be moved to the Zero (travel start) position. Then depress the ZERO button until the lower green LED flashes once, or send the appropriate command via the RS-485 port. The flash of the LED indicates that the Zero position calibration has been accepted. If an error occurred and it is desired to set the Zero point again, depress the ZERO button again and the Zero point calibration will be updated with the new position as indicated by another flash of the lower green LED.

Full Scale is set

Full Scale set required

Zero set required

Zero is set

Table 5. LEDs in CALIBRATION mode. LEDs flash if Full Scale reset or Zero reset is required.

If the LVDT’s calibration was successful and the DSP was able to be properly scaled, then the green LEDs will not be blinking. In the event that something unusual has caused the calibration to be rejected (such as a very high or very low output LVDT), either the upper (Full Scale) or lower (Zero) LED, or both, may be flashing again. This means that the core must be moved to that particular position again, and re-scaled or re-zeroed by repeating the original Full Scale and/or Zero calibration procedures.

Normally, repeating the calibration process one time will remedy any problems that have developed during the DSP's auto-scaling operations.

When the calibration is completed, exit the CALIBRATION mode by depressing both the FULL SCALE and ZERO buttons simultaneously until the red POWER LED stops flashing and glows steadily. There is also an RS-485 command for exiting the CALIBRATION mode. After exiting CALIBRATION mode, the module will return to normal operation in RUN mode, the red POWER LED will glow steady, and the green function LEDs (except for the master module in a master/slave configuration) will not be glowing.

Live Zero and Extra-range Output When a unipolar DC output range is selected, the Full Scale and Zero positions correspond exactly to that range. But to have a "live zero output", the DC output is capable of going higher and lower than these points by 2.5 to 3%. So, for example, with a 0 to +10 V full scale output, the output continues to go past the Full Scale and Zero calibration points, going up to about +10.3 V or down to about -0.3 V.

For current loop output, the output continues from 0.4 mA to 0.6 mA past the calibration points. For a 4-to-20 mA output (span = 16 mA), it continues to respond up to 20.6 mA and down to 3.6 mA. These limit values can vary a little bit from module to module, depending on circuit and component tolerances.

Using the Voltage and Current Outputs When in any of the voltage output modes, the output current to the load resistor is normally just a fraction of one mA, but should always be less than 5 mA .The recommended minimum load resistance across terminals J3-4 (+ output) and J3-3 (- ground) for any of the voltage outputs is 10,000 Ohms.

When using a current loop output, either 0 to 20 mA or 4 to 20 mA, the maximum loop load resistance permitted depends on the power supply voltage, as shown in Figure 5 below. When the module is powered from the recommended 24 Volt DC supply, the maximum loop load resistance is 850 Ohms.

Typical loop loads are 250 or 500 Ohms, so this gives adequate capacity for long connecting lines.

Figure 5. Maximum Loop Load Resistance vs. Supply Voltage

Failure Diagnostics The S1A module incorporates diagnostics to identify internal failures, mistakes made during the setup, and operational failures due to external causes, providing failure indication both visually and electrically.

When the S1A is in RUN mode, the front panel LEDs indicate specific operational failures by flashing at a rate of 0.1 second on and 0.1 second off, according to Table 6. Setup errors are typically indicated by steady on LEDs, and multiple failures are indicated by an LED that alternates between blinking and steady on. When indicating a "general failure" in RUN mode, the red POWER LED will flash at the same rate of 0.1 second on and 0.1 second off. (It flashes at the slower rate of 0.5 second on and 0.5 second off while indicating that the S1A is in CALIBRATION mode.)

RUN

MODE

Normal Operation

Master Operation

Primary Open

Secondary Open

LVDT not Connected

Excitation Error

Shorted Sync Line

Frequency Set Error

General Failure

POWER

P ○ ○ ○ ○ ○ ○ E ○ ○ ○ ○ ○ ○ ○ S ○ ○ ○ ○ ○ ○

Table 6. ☼ indicates a flashing LED. Most failure modes flash the LEDs, but some are steady on

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In addition to the local visual indication of a failure or fault by LEDs as illustrated by Table 6, the S1A also provides electrical outputs that allow the failure warning to be transmitted to a remote indicator, system controller, or other device. These electrical outputs include an open collector failure warning flag output, out-of-range analog outputs, and various error codes accessible via the RS-485 digital bus.

A table identifying the meaning of these digital error codes is listed in Appendix A, which also lists possible multiple failures or faults beyond those shown in Table 6 that can be indicated by the LEDs.

Failures identified by the diagnostics incorporated in the S1A can be classified either as errors in setting up the module during installation that should be corrected before the S1A module is brought online, or operational failures that occur sometime after the module has been properly installed and put into service. The module may produce different outputs for each of these two different classes of failures, as explained below.

If a "general failure" occurs, it might require powering the module down and back up to clear it. While the power is off, the user should recheck the wiring to or from the LVDT and the module, and the wiring between multiple modules operating in master/slave mode.

Failure Warning Flag When any of the operational failures shown in Table 6 occur, the DSP activates the continuous output failure warning flag via an open collector transistor output that can operate a relay, alarm, or use a pull-up resistor for a TTL output pulse. This failure warning has a short delay before activation to eliminate trips due to momentary effects such as power line noise spikes, nearby lightning strikes, and similar transients. If set up errors shown in Table 6 occur, the failure warning flag output may not be activated, because all set up errors must be corrected before the S1A module can function properly, including its ability to set the continuous output failure warning flag.

Failure Warning by Out-of-Range Analog Output Besides the continuous output failure warning flag using an open collector transistor, the S1A module also offers another form of electrical failure notification by driving the analog output to an out-of-range value of voltage or current. This out-of-range signal is usually a slightly negative output, although in the case of the ±10 V DC output, failure is indicated by a greater negative output than -10 Volts DC.

Unlike the open collector output failure flag, the out-of-range output has no built-in delay, so it can react to some transient effects. This is because many applications that utilize the S1A module with redundant sensors incorporate a voting scheme to either assess the fidelity of the multiple readings or average the readings from the multiple sensors to derive some acceptable value. Typically the controllers used with redundant systems sample the sensors' output levels at high speeds with internal diagnostic software that rejects an output value that either goes out of range or that deviates too sharply from an expected value. A very fast fault or failure response that shifts the S1A's analog output out of range works with the software to prevent an erroneous output from being averaged or accepted in the voting scheme.

Alternative Calibration Procedure For some specific applications, there is an alternative calibration procedure that can often save time by establishing the mechanical relationship of the LVDT's core to the workpiece whose motion is being measured without going through the process of actually finding the LVDT's null point. This process can work well in cases where the nominal range of the LVDT is at least 10% larger than the range of motion of the workpiece to be measured. It works by connecting an ungrounded DC voltmeter with a range of about 0 to ±3 Volts to terminals J4-1 and J4-2, the Null Indicator output for a continuous indication, recalling that each terminal is floating with respect to common ground. (Refer to page 9)

Mechanically connect the LVDT core to the workpiece at about the middle of its range of motion. Move the workpiece to each end of its range of motion, noting the voltage indicated on the meter. Adjust the core's position so that the output of the voltmeter at each end of the range of motion is approximately the same, thereby establishing that the LVDT is operating in a symmetrical manner within its nominal range of measurement. Now proceed to calibrate the system's Zero and Full Scale as noted on page 9.

The LVDT’s core must not protrude from the LVDT during any of the measurements or errors will result.

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Troubleshooting LVDT Connections Table 6 on the previous page shows the S1A front panel LEDs indicate most common LVDT wiring failures. If a front panel LED indicates an open winding, turn off the DC power and troubleshoot the LVDT wiring with an ohmmeter. Double check the LVDT’s lead wire colors or connector pinouts against the specifications for that LVDT in order to make sure that all of the wires are correctly identified and properly connected. When running cables between LVDTs and signal conditioners, the most common wiring errors are a disconnected LVDT primary lead, a disconnected secondary lead, or a failure to properly connect the two secondaries together. This latter issue occurs quite often and should be checked first and foremost.

In the S1A, the secondaries of the LVDT are connected together in a series-opposing configuration. It is strongly recommended that the interconnection of the secondaries be done at the LVDT itself, before any cabling or wiring is attached. Normally, the junction of the two secondaries is not connected to the LVDT signal conditioner at all. However, when an S1A is hooked up in close proximity to the LVDT, the secondary junction connection may be hooked up to J2-1, which is merely a convenient tie point not connected to anything within the signal conditioner. With a long cable run between the LVDT and the module, the secondary interconnection absolutely should be made at the LVDT, not run back to the module. Note that the S1A signal conditioner does not utilize each individual secondary's signal, but only operates on the net differential AC output that results from the series-opposing winding configurations, as shown in Figure 4 on page 4.

Grounding and Shielding The most common problem encountered with grounding and shielding of a sensor circuit is current flow in the ground circuit, called a ground loop. To avoid ground loops, only one place in the circuit must be the common ground point, which is usually at the signal conditioner module. All of the ground wires should run from that point. When an AC ground current flows in a shielded wire, the shield current could induce unwanted voltages into the signal wires contained inside, so do not connect the shield to the sensor’s housing or to any separate ground point. Connect it as a Faraday shield to the ground point.

Commands for the RS-485 port Commands for transmission via the RS-485 communications link can be sent to an S1A using a program such as Hyper Terminal, available in all versions of MS Windows™ software, and an RS-485 port adapter. Communication parameters are: half-duplex mode, 9600 bps, no parity, 8 data bits and 1 stop bit (9600, NP, 8,1). Note that all commands must be preceded by a signal conditioner address in the format: Uxx, where xx is a number from 00 to 15, which is the identity address of the specific module as set using Table 1a.

Cal Enters CALIBRATION mode; same as pressing FULL SCALE and ZERO pushbuttons together.

Config Lists all the setup data with their DIP switch settings or present values: output DIP setting (1-8), excitation frequency DIP setting (1-4), address (00 -15), invert (on or off), low frequency filter (on or off), EEPROM values: ADC hi, ADC lo, input pot value, gain pot value. (Log all "Config" names and values for possible future reconfiguration) Exit Required to exit any command, and to write any value to the EEPROM in the "Cal" mode FS In "Cal" mode, sets full scale position of the core; same as pushing the FULL SCALE pushbutton L Outputs the present LED status. In "Cal" mode, "L" may be sent several times for the DSP to send the present status of the 3 green LEDs. e.g. xxo means first and second LEDs are on.

Read Analog returns the nominal value of the analog output, depending on the setting of S1 Read FS Returns present DAC input value for Full Scale point (log value for future reconfiguration) Read Z Returns present DAC input value for Zero point (log value for future reconfiguration) Set ADC Hi In "Cal" mode, sets high value of Analog to Digital converter input during reconfiguration Set ADC Lo In "Cal" mode, sets low value of Analog to Digital converter input during reconfiguration Set FS In "Cal" mode, sets value of DAC Full Scale point input from logged value for "Read FS" Set Gain In "Cal" mode, sets value of gain pot logged from "config" command for reconfiguration Set In Pot In "Cal" mode, sets value of input pot logged from "config" command for reconfiguration Set Z In "Cal" mode, sets value of DAC Zero point input from logged value for "Read Z" Z In "Cal" mode, sets the zero position of the LVDT's core; same as pushing the ZERO pushbutton

S1A Specifications

Operating power: +15 to +32 V DC (+24 V DC nominal), 60 mA max. at 24 V DC;

+15 V DC and -15 V DC for -10 V to +10 V DC bipolar output LVDT excitation voltage: 3.0 Vrms sine wave push-pull drive nominal (factory default)

4.5 Vrms sine wave push-pull drive via on-board J7 jumper shift

1.5 Vrms single ended drive for low impedance (100 -150 Ω) primary Excitation frequencies: 1 kHz, 3 kHz, 5 kHz, 10 kHz (nominal) External synchronization: Master output couples up to fifteen slave inputs; if original master fails, new master is automatically generated for fail-safe excitation control.

LVDT AC output signal: 50 mVrms to 5000 mVrms at LVDT's full scale position Analog DC outputs: 0 - 5 V, 1 - 5 V, 0.5 - 4.5 V, 0 -10 V, -10 to +10 V, 0.5 - 9.5 V, 0 -20 mA sourcing, 4 -20 mA sourcing Loop resistance: 850 Ω max. with 24 V DC supply Output non-linearity: ≤0.025% of Full Span Output (FSO) Frequency response: -3 dB at 10% of excitation frequency (nominal) (standard: DS2-4 off) -3 dB at 10 Hz (nominal) (low noise setting: DS2-4 on) Noise and ripple: ≤2 mVrms (voltage output), or ≤4 µArms (current loop output.)

Fault indication: Loss of excitation, primary open, secondary open, LVDT disconnected Fault output: LED indicators, open collector output, 50 mA, 26.5 V DC max.

Null detection: Front panel LEDs, ± 30 mV threshold out of ≈±1.6V signal level Null output: LEDs, DC null voltage signal (≈±3 V DC = ±FS) Operating temperature: -20 ºC to +75 ºC Zero set: Front panel push button or RS-485 command Full Scale set: Front panel push button or RS-485 command Digital interface: RS-485 2-wire multi-drop network, 16 individual addresses

S1A Module Outline Dimensions

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EC Declaration of Conformity

The undersigned, representing Everight Sensors Corporation, 102 Commerce Drive, Suite 8 Moorestown, New Jersey 08057 USA hereby declares that the product, Model S1A LVDT Signal Conditioner, of the following category and type, Measurement, Control Equipment, and Laboratory Use, is in conformity with the provisions of the following EC directive(s): EMC Directive 2004/108/EC.

Testing was done to requirements as stated in harmonized standards EN 61326-1: 2006 and CISPR 11, A-1: 2003 using the methods noted hereafter: IEC 61000-4-2: 2001, IEC 61000-4-3: 2002, IEC 61000-4-4: 2004, IEC 61000-4-5: 2001, IEC 61000-4-6: 2003, and CISPR 11 A-1: 2003.

A TCF for the product is maintained for inspection at the location noted.

Edward E. Herceg June 1, 2009 Edward E. Herceg, VP, CTO Date of Issue

Product Warranty

Everight Sensors Corp. warrants the Model S1A LVDT Signal Conditioner to be free from defects in workmanship and materials for a period of two (2) years from the date of shipment. In the event a valid claim is made under this warranty, the only obligation of Everight Sensors Corp. is to repair or replace the unit. Under no circumstances will Everight Sensors Corp. be liable for fitness of purpose by the user or any damages, direct, consequential, or otherwise, or for any damage to any sensor connected to the S1A LVDT Signal Conditioner, or for any damage to any electronic equipment connected to the input or outputs of the S1A LVDT Signal Conditioner.

To submit a claim under the provisions of this warranty, the claimant must secure an RMA (Returned Material Authorization) number by contacting Everight Sensors Corp. at: 856-727-9500, or by sending a letter, or e-mailing info@everightsensors.com. The defective unit must be returned freight prepaid to Everight Sensors Corp. for inspection, accompanied by the RMA number and a letter of explanation of the purported defect. If the inspection and evaluation validates the warranty claim, a repaired or replaced unit will be promptly returned to the claimant freight prepaid.

If inspection and evaluation of the device determines that it has been misused, abused, misapplied, or modified by the user; has been subjected to a fire, flood, or mishandling; or is damaged due to improper packing for the return shipment, no warranty claim will be allowed or accepted. Instead, the unit will be returned to the claimant freight collect, along with an invoice for the evaluation charge. Any questions about Everight's warranty provisions can be answered by contacting Everight Sensors Corp. at: 856- 727-9500, or by sending an e-mail query to: info@everightsensors.com.