Attachment C - Specification Document.docx

ASOS Precipitation Accumulator (PA) Specifications Document - July 26, 2023

1. Requirements

1.1. General Requirements

[PA-4] The vendor must provide detailed sensor disposal instructions in accordance with the Pollution Prevention Act of 1990.

1.2. Precipitation Liquid Water Equivalent (LWE)

[PA-5] The PA must have automated capability to measure all freezing and frozen precipitation types including the LWE contribution of different precipitation types during mixed precipitation events.

1.3. Mounting

[PA-6] The Contractor shall ensure the PA sensor mounts to the standard ASOS pedestal, which consists of a standard class 150 galvanized steel flange (four bolt pattern) mounted on an 18-inch-high length of 3-inch nominal schedule 40 pipe. The Contractor must evaluate the ability of this mounting pedestal to be used with the PA. If the Contractor establishes that the PA cannot be mounted on the standard ASOS pedestal, the Contractor may, with written Government concurrence, also make use of concrete piers installed at ASOS PA sites. The specifications for these piers and their relative location to the standard mount location are shown in Figure 1 below. The Contractor must notify the Government if use of these piers is required. The Contractor must provide all necessary hardware to mount the PA to the standard ASOS pedestal and/or the concrete piers. All mounting hardware must be 316 or better stainless steel.

Figure 1 - Concrete Piers

1.3.1. Surrounding Obstructions

[PA-7] The PA Sensor must meet the Performance Requirements in Section 1.5 when installed in the meteorological shadow of ambient temperature and dew point temperature sensors located 48 inches to the east of the PA and which are approximately 24 inches wide extending from 48 inches above the ground to 70 inches above the ground.

1.3.2. Sensors proposed with Wind-Screens

[PA-8] The Vendor may propose a wind-shield for each PA in order to meet accuracy requirements. The vendor shall be responsible for determining wind and ice loading requirements for their proposed wind-shield. A single wind-shield shall be used in all geographic locations. The PA shall be provided with all mounting hardware for the wind-shield.

The wind shield shall:

[PA-9] Adapt to the existing concrete piers depicted in figure 1 of this specification document.

[PA-10] Be corrosion and UV resistant; made of galvanized or stainless steel, or aluminum; wind-shield made of other materials will be evaluated for durability, longevity and service life at the government’s discretion.

[PA-11] Allow for routine gauge maintenance and replacement.

[PA-12] Have appropriate manufacturer warning signs attached.

[PA-13] Be a maximum of four (4) feet in diameter when installed centered on the PA sensor pedestal.

1.4. Self-Testing/Diagnostic Capability

The maintenance philosophy of the ASOS is to maximize the ability of today’s “smart” sensors to perform built-in tests capable of detecting and reporting internal anomalies and/or failures which adversely impact reporting accuracy. The Government will maximize this built-in test capability. As a goal, the PA will be capable of identifying and fault-isolating all sensor-specific hardware and software anomalies.

[PA-14] The Contractor must identify the extent to which the PA can provide these capabilities and must provide an interface document which details all communication and message formats relevant to this capability.

[PA-15] Extended diagnostic procedures must be provided for faults that cannot be detected by the self-testing/diagnostic capability.

The extended diagnostics are diagnostic procedures designed to be performed through external commands received via a maintenance technician laptop computer connected to the serial interface of the gauge. These diagnostic procedures may make use of extensive dialogue with the maintenance technician, and may use commonly available external test equipment and/or common hand tools if required.

1.5. Performance Requirements

1.5.1. Capacity

[PA-16] The PA must have a minimum capacity of forty (40) inches of liquid water equivalent without the need for maintenance actions to empty, reset, or otherwise perform any action on the gauge. This capacity is exclusive of the additional capacity required in the case of a gauge using antifreeze to eliminate the effects of evaporation. This requirement does not apply to self-emptying technology. i.e. Flow meter, tipping bucket, forward scatter etc.

1.5.2. Resolution

[PA-17] The PA must have a minimum reporting resolution of 0.01 inch of liquid water equivalent. Incremental accumulations from one minute to the next, which are less than 0.01 inch, must be accumulated and summed internally by the PA, and must be reported whenever the threshold of 0.01 inch is reached.

1.5.3. Starting Threshold

[PA-18] The PA must have a maximum starting threshold equivalent to 0.01 inch of liquid water equivalent.

1.5.4. Accuracy

[PA-19] The PA sensor must perform in a linear fashion over a rain rate of .01 to 10 inches per hour, the measurement range, with an accuracy of ±4% or ±0.02 inch, whichever is greater.

[PA-20] The PA must not falsely report (report accumulation in the absence of precipitation) more than 0.09 inches for a single, continuous 30 day period. The goal is that there be no false reports.

[PA-21] It is recognized that smoothing or filtering algorithms may be required in order to reduce false precipitation reports. If such algorithms are required, the maximum acceptable delay reporting precipitation due to filtering must be five (5) minutes.

1.6. Interface Requirements

[PA-22] The PA Sensor must be capable of interfacing with the CSI, CR1000X Datalogger and have a built-in asynchronous data interface mode capable of any of the following: an SDI-12, RS-232 or RS 485 interface with user-selectable baud rate, parity, data bits, and stop bits.

1.7. Power Requirements

[PA-23] The PA Sensor must operate using a power supply that operates with an input of 115 Vac ± 10%, 60 Hz, and less than 5 amps for AC power OR 12-24VDC, and less than 15 amps for DC power. Optional heaters can operate at 12 or 24V DC.

1.8. Environment Requirements

1.8.1. Temperature

[PA-24] The PA Sensor must be able to maintain operations in temperatures up to 120o F.

[PA-25] The PA Sensor must be able to recover operations from temperatures up to 130o F.

[PA-26] The PA Sensor must be able to maintain operations in temperatures down to -40o F (-60o F preferred).

[PA-27] The PA Sensor must be able to recover operations from temperatures down to -80o F.

[PA-28] The PA Sensor must be able to maintain operations in temperature shock conditions dropping from 70o F to -40o F (-60o F preferred).

[PA-29] The PA Sensor must be able to recover operations from temperature shock conditions dropping 70o F to -80o F.

[PA-30] The PA Sensor must be able to maintain operations in temperature shock conditions increasing from 80o F to 120o F.

[PA-31] The PA Sensor must be able to recover operations from temperature shock conditions increasing 80o F to 130o F.

1.8.2. Humidity

[PA-32] When operating in ambient air temperature conditions less than or equal to 80oF, the PA Sensor must operate without performance degradation in ambient relative humidity conditions up to 100% RH.

[PA-33] When operating in ambient air temperature conditions within the range of 81oF to 95oF, the PA Sensor must operate without performance degradation in ambient relative humidity conditions up to 95% RH.

1.8.3. Wind

[PA-34] The PA Sensor must operate without performance degradation when exposed to one-minute sustained average wind speeds up to 43 knots.

[PA-35] The PA Sensor must operate without performance degradation when exposed to one-second wind gusts to 62 knots.

1.8.4. Rain

[PA-36] The PA Sensor must operate without performance degradation when exposed to rain falling at a minimum rate of at least 3-inches per hour with up to 30-knot wind speed conditions.

[PA-37] The PA Sensor must be able to recover operations from rain conditions of at least 5 inches per hour with 73-knot winds.

1.8.5. Freezing Rain

[PA-38] The PA Sensor must be able to maintain operations in freezing rain conditions of ice accretion 0.5 inches per hour up to 1.0 inches with 20-knot winds.

1.8.6. Other Environmental Elements

[PA-39] The PA Sensor must be able to maintain and recover operations from exposure to dust conditions up to 5.0 mg/ft3 with winds of 2.6 knot to 4.3 knots [PA-40] The PA Sensor must be able to maintain and recover operations from exposure to atmospheric pressures as low as 15.7 inches of Hg.

[PA-41] The PA Sensor must be able to maintain and recover operations from exposure to the electromagnetic environment of a typical airport.

[PA-42] The PA Sensor must be able to maintain and recover operations from exposure to salt fog characteristic of a typical marine environment.

1.9. Warranty

[PA-43] The contractor shall provide a warranty for each PA Sensor. Warranties shall begin upon Government acceptance at NLRC. The contractor shall repair or replace all units that fail for the duration of the warranty at no cost to the government. The warranty shall include shipping, labor, and parts. The warranty period will be defined as part of the proposal. Extended warranties are encouraged.

1.10. Delivery

[PA-44] Delivery of each order placed shall occur no later than 60 days after receipt of individual delivery orders placed off the base contract. The Contractor will provide documentation of current practices in place to pack, ship, and protect the units during transit to the following location:

NOAA National Logistics and Reconditioning Center (NLRC) 14200 Merritt Rd Grandview, Missouri 64030

In addition, each shipping package shall contain the CAGE code, Part number, Item description, Quantity, and Delivery Order number, Gross weight and mark any HAZMAT material as applicable per MIL-STD-129M standards.

*Note: For evaluation purposes, the vendor must be able to meet a delivery of 95 precipitation accumulators in 60 days.

image1.png image2.png image3.png