[PSUBS-MAILIST] Pressure Transducer

[Sean T. Stevenson via Personal_Submersibles]

Jon - What are the specs on your SSI transducer? Are you using voltage, current or unamplified? 15 bits on 500 psia should give you 0.01526 psi resolution, provided the input range of your signal conditioner matches the output range of the transducer. Check that. There could be a range mismatch, and possibly a unipolar / bipolar mismatch which would double the achievable step size (e.g. if that 15 bits corresponds to -10 V to 10 V, but the transducer signal is unipolar etc.).

You will likely see some temperature drift if the transducer is not temperature compensated within the range of service conditions, and I would also check for grounding of the transducer body, and shielding of the signal cable if it is not 4-20 mA.

If it is a current transducer, is it loop-powered or independently powered? If it is amplifed (voltage or current signal), check the stability of your power supply. If it's a bridge, that's even more critical. On the signal processing side, check how you are obtaining the reading. Acquisition frequency of the ADC vs display update frequency, etc. It could be that a lowpass filter on the measurement will make it behave better.

Sean

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, July 22, 2020 7:11 AM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

> Sean,
>
> I think you've talked about sourcing pressure transducers in the past, do you have any recommendations for ones that you have found reliable? I'm getting quite frustrated trying to interface the SSI Technologies P51 series with a 16-bit ADC (using 15 bits) and unable to get results that are anywhere close to my calculated/expected results even considering worst case accuracy limits. I don't mind paying more for a sensor that is going to perform close to it's datasheet specs. Specifically, looking for 500 psia with .5% or better accuracy. I'd prefer .25% or better accuracy but can live with .5%.
>
> Jon
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