SATPC0041944 Tab 04 4 SPECS..pdf
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- Custom 3-channel constant-temperature-anemometer (CTA) system Federal contract opportunity
- Solicitation number
- 80NSSC26939337Q
About this file
This document is a general specifications proposal for a three-channel Constant Temperature Anemometer (CTA) System developed by the LaRC group, dated 13 July 2026, based on original 2023 specifications.
The CTA system specifications detail probe sensor resistances ranging from 2 ohms (platinum-plated tungsten) to 10 ohms (platinum-rhodium Wollaston wire) at cold state, with maximum values reaching approximately 20 ohms at an overheat ratio of 2.0. The system must operate across probe environments from 60 to 500°F with bandwidth capability up to 400 kHz and cable lengths optimized for 20-30 meters using RG58 type cable and RG178 type leads, both with 50 ohm impedance. The CTA system shall operate on a 1:1 bridge ratio with an external arm to balance the probe arm, and include an oscillator with both internal square wave injection and external signal injection capability featuring a voltage divider for standard waveform generator compatibility. Noise performance must be low, with voltage noise due to the amplifier matching the Johnson noise of the probe resistor in the bandwidth of interest, demonstrating predictable f^2 noise behavior at high frequencies. The overall system shall consist of three CTA channels with cabled connections to a Power Supply/Oscillator module, similar to the original 3-channel CTA system design. Minor enhancements include minimizing temperature sensitivity of gain adjustment components and implementing a method to identify inductor settings for quick and repeatable adjustments.
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Other files for this federal contract opportunity
| File | Type | Posted |
|---|---|---|
| SATPC0041944 Tab 04 4 SOW..pdf | ||
| SATPC0041944 Tab 06 RDSS..pdf | ||
| SATPC0041944 Tab 07 Capability Statement.pdf |
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Text version
Constant Temperature Anemometer (CTA) System
General specifications proposed by LaRC group for a 3-channel CTA unit (based on original specs from 2023)
13 July 2026
1) Probe sensor resistances: 2 ohm (platinum-plated tungsten) – 10 ohm (platinum-rhodium Wollaston wire) cold. Maximum value at overheat ratio of 2: ~20 ohms. The cable + lead resistance is typically between 2.5 and 2.6 Ohms. The cable lengths (RG58 type cable) are typically 20 to 30 m. The leads lengths (~0.060” dia coax cable or RG178 type cable) are typically between 50 to 64”. Both cable and lead are 50 Ohm impedance.
2) Maximum overheat ratio: Rhot/Rcold = 2.0.
3) Probe operating environments: 60 to ~500 F.
4) Bandwidth: capable of bandwidths up to ~400 kHz.
5) Cable lengths: design for 20-30 meters to achieve optimal performance at these lengths. The system should still work with longer or shorter cables, so we should have enough latitude in the system adjustments, but the achievable frequency response may be impacted. The 1:1 bridge is supposed to be fairly forgiving of different cable lengths assuming the probe and external arm are well matched.
6) Bridge ratio 1:1: operate with an external arm (comprised of a cable, lead, and manually adjustable resistor) to balance the probe arm (comprised of a matched cable and lead, and a hot-wire sensor). Top of bridge resistors equivalent on the passive and active legs of bridge.
7) Oscillator: in addition to internal square wave injection, add ability to inject external signal to enable manual tuning of frequency response. For external injection and small amplitude values required for injection, add feature like a voltage divider to enable the use of standard waveform generators without external amplitude attenuation.
8) Noise: Low. (Target voltage noise due to amplifier of same order as Johnson noise of probe resistor in bandwidth of interest). If everything is done right, the system noise can be predicted on the basis of the Johnson noise associated with all the resistors in the system and the amplifier noise. The minimal achievable noise goes as f^2 with frequency. If we see that behavior, we know the system has been well designed. At high frequencies the signal is dominated by the f^2 noise.
9) CTA system: System to consist of three CTA channels with cabled connections to a Power Supply/Oscillator module. The overall system shall be similar to the original 3-channel CTA system.
10) Minor tweaks to original 3-channel CTA system (nice to haves): a) minimize the temperature sensitivity of the gain adjustment to the time the bridge is activated, i.e., reduce the temperature sensitivity of components used to set the system gain. b) Implement a method to identify inductor setting for quick and repeatable inductor adjustments.
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