Amendment QAs.pdf

Question 1:

The SoW mentions specific requirements for input and output modules but does not have these requirements for strain bridge modules. A subsequent statement refers to strain gauge inputs, though (“Capable of measuring all the analog inputs, strain gauge inputs, thermocouple inputs, and digital inputs, simultaneously, while also simultaneously outputting all the analog and digital outputs.”). Could you provide requirements for the strain gauge inputs as well? For example, sample rates, bridge configurations, etc.

Response to Question 1:

“strain gauge inputs” is a mistake. No strain gauge inputs are necessary. The Attachment A – Statement of Work (SOW) has been revised.

Question 2:

To which channels do the digital filtering requirement apply? All analog inputs? Or only a subset?

Response to Question 2:

All the analog inputs and thermocouple inputs shall be capable of digital filtering (e.g., IIR type).

The instrument shall have a latency between the measured analog inputs and PID control analog output equal to 100 microseconds (or less) for 4 simultaneous PID control loops. The latency also includes performing real-time digital filtering of the analog inputs before updating the PID output.

Question 3:

The SoW states that the digital outputs are sourcing outputs but does not state if the digital inputs are sinking or sourcing. Can you clarify?

Response to Question 3:

Digital inputs can be either sinking or sourcing.

Question 4:

The FPGA will need to be sized based on the workload. It is unclear what the FPGA will be required to do, but we can assume that it may be acquiring data, calculating multiple PID control loops, and possibly filtering data. The price difference between various FPGAs can be large.

Should we assume that NIST would like the largest FPGAs available, or can we get more detail on the FPGA’s role?

Response to Question 4:

The FPGA shall be sized to meet the Hardware Requirements. For example:

1) Measure and record all the analog inputs, thermocouple inputs, and digital inputs, simultaneously, while also simultaneously outputting all the analog and digital outputs.

2) Achieve latency requirements of 100 microseconds (or less) for 4 simultaneous PID control loops on digitally filtered (e.g., IIR type) analog inputs signals. The latency also includes performing real-time digital filtering of the analog inputs before updating the PID output.

Question 5:

Can you provide more detail on the digital filter specification? The SoW states: “filtering at cut-off frequency (-3 dB) range between at least 45 % the sampling rate or less.” Can you specify if this is the sample rate of the thermocouples, the analog inputs, the strain channels, or all of the above?

Response to Question 5:

Digital filtering (IIR type or similar) shall be programable depending on the acquisition rate. For example, 50 thousand samples per second * 0.45 = 22.5 kHz cutoff frequency (-3db) for the analog inputs. The thermocouple inputs shall have a different cutoff frequency due to the acquisition rate (1500 S/s*0.45 = 675 Hz cutoff frequency (-3db)). Regarding strain gauge channels, see Question 1.

Question 6:

Since thermal systems are generally slow, how critical are the requirements for the thermocouple channels to be simultaneously sampled at 1.5 kHz?

Response to Question 6:

As reported in the requirements, the 8 fully isolated thermocouple inputs shall be capable of sampling rates of 1500 samples per second per channel simultaneously (or more).

Question 7:

Is there a required bit depth for the thermocouple measurements?

Response to Question 7:

The bit depth for the thermocouple measurements shall be sufficient to achieve a resolution of

0.1 degree C within the complete temperature range for thermocouple Type K, Type J, and Type R.

Question 8:

What are the logic levels required for the digital inputs & outputs? 24 VDC, TTL, etc.?

Response to Question 8:

A wide range of logic level inputs (3.3 VDC to 24 VDC) are preferred. The digital inputs and outputs shall be capable of 5 VDC.

Question 9:

Are digital inputs and outputs being sampled on demand or hardware-timed?

Response to Question 9:

Hardware-timed digital inputs and outputs is preferred, but either software or hardware-timed digital inputs and outputs are acceptable if the rates requirements are met (see hardware requirements).

Question 10:

Does NIST need calibration services for this instrumentation? Vendors provide service plans for calibration, but on the other hand, I can imagine that NIST is more than capable of doing this calibration internally.

Response to Question 10:

The device shall be calibrated with certificates prior to arrival. However, a calibration service plan is not in the requirements.