[PSUBS-MAILIST] Pressure Transducer

Wed Jul 22 12:24:55 EDT 2020

I should add to that - we have an in-house calibration lab, so we don't bother with more than the basic factory calibration on ordering transducers, because we reperform the calibrations on arrival anyway. If you are relying on factory or third-party lab calibrations, it may be worth it to pay for the expanded 5 or 10-point factory calibration option, if you care about your measurement being traceable / minimizing error. For a personal project in which traceability didn't matter, five years would still be about my comfort limit for calibration interval. These transducers are all subject to a bit of zero offset drift over time. There is always some production variance, and interestingly, in the case of the Honeywell STJE's (0.05% published accuracy), I heard from the rep that these are simply TJE's which happened to test out with tighter accuracy, so they get the STJE label.

Sean

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On Wednesday, July 22, 2020 10:12 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

> I use a lot of pressure transducers, which I divide roughly into two categories: 1) Pressure transducers which are for the sole purpose of monitoring machine / system parameters for operator or diagnostic feedback, and 2) Pressure transducers which will directly produce client data. For the former purpose, I will buy any transducer with appropriate datasheet specifications, and may source from Omega, Digi-Key, or any of the instrumentation providers who may rebrand Chinese transducers, because I need neither accuracy nor traceability (nor technically, reliability). Anything that can fail without severe consequences is in this category, and I tend to go cheap on. That said, all transducers are subject to in-house calibration, and a two-point verification (typically at 20% and 80% of range) against a traceable standard. I don't care if there is some error, but I do need to characterize it to know what my absolute accuracy actually is.
>
> For the latter purpose, I buy almost exclusively from Honeywell, but may occasionally buy from Wika or other established manufacturers. These transducers are independently calibrated in a pressure, temperature and humidity controlled laboratory in both directions, are traceable with known accuracy to NIST standards, and the drift across subsequent calibrations can be tracked (typically at 6 month to 1 year intervals). If such a transducer is within its calibration interval, I will install it in a system, subject to the same two-point verification process before any data is used. If the calculated error on verification (both % of reading, and % of full scale) is greater than either the published specs or the calibration data, it goes back for calibration. If it won't calibrate within specs, it goes for repair / replacement.
>
> Specifically, I would suggest that you look at the Honeywell FP2000 or FP5000 series transducers, which are available as mV/V bridge, or amplified voltage or current outputs. I use a lot of 4-20 mA FP5000's. I'm not sure how you are conditioning / using the output signal in your application? (I also use TJE / STJE series mV/V transducers, but usually only for pressures greater than 10,000 psi. I have a couple of 50,000 psi TJE's, and these track pretty reliably over a 5000 psi FP2000 on the same source). The FP2000 / FP5000 series are cheaper (but not cheap!), and more than good enough for every purpose I have encountered so far. You can find the datasheets for these online. They are configurable, so you specify all options (range, gauge/absolute/differential, amplifier type, temperature compensation, material, connector type, etc.) per the datasheet info and then get a quote for your desired part number(s). They are built to order, so typically a few weeks lead time. I purchase mine through Hoskin Scientific, but you may have different local distribution. Again, probably closer to $1000 than $100, but when accuracy / reliability count and the information is critical, going cheap doesn't save you anything.
>
> 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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