Electronics > Metrology

Calibration of a Fylde FEH379TA Amplifier

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mendip_discovery:
So I have been asked to take a look at some Fylde Amplifiers for a customer. You know the type of job, office says "Yeah we can do it", engineers look on in horror.

I am guessing they are these,
https://www.fylde.com/wp-content/uploads/2018/03/FEH379TA.pdf

A quick guess I would be looking at confirming the Voltage output is still good and stable. Also potentially inset some Hz to see if the filters are still functioning. I think it is a bit daft to have me calibrate these as they are the kind of item that if they are not working it is going to be pretty obvious at the scope that there is noise/error but I have been asked to calibrate them.

RandallMcRee:

--- Quote from: mendip_discovery on July 31, 2021, 06:24:32 pm ---So I have been asked to take a look at some Fylde Amplifiers for a customer. You know the type of job, office says "Yeah we can do it", engineers look on in horror.

I am guessing they are these,
https://www.fylde.com/wp-content/uploads/2018/03/FEH379TA.pdf

A quick guess I would be looking at confirming the Voltage output is still good and stable. Also potentially inset some Hz to see if the filters are still functioning. I think it is a bit daft to have me calibrate these as they are the kind of item that if they are not working it is going to be pretty obvious at the scope that there is noise/error but I have been asked to calibrate them.

--- End quote ---

You've stepped into it. If I was the customer I would now expect that you would confirm the main specs given in the data sheet:
The pre-amplifier has gain calibrated from 1mV to 1V for full scale output, and features high stability and linearity,
good CMRR and wide dynamic range.
and
Linearity <0.02% deviation.
Accuracy ±0.25%.
Stability 0.02% - 12 months.
also noise, and a few other things.
Maybe set some expectations between you, the customer and your management ??  ::)

Neomys Sapiens:
Nope. You respectively your company can be held liable for this. You are not able to CALIBRATE those amplifiers until you know the cabration procedure and have the suitable normals and parts. This is a very different thing to a function check and even a performance check. The latter is what you could do in a normally equipped lab. You should point that out and not give in.

mendip_discovery:

--- Quote from: Neomys Sapiens on August 03, 2021, 03:09:33 am ---Nope. You respectively your company can be held liable for this. You are not able to CALIBRATE those amplifiers until you know the cabration procedure and have the suitable normals and parts. This is a very different thing to a function check and even a performance check. The latter is what you could do in a normally equipped lab. You should point that out and not give in.

--- End quote ---

As the calibration engineer, it is my task to work out how to calibrate an item and then produce a procedure from that. I'm not doing adjustments, just a calibration. There are lots of items that look complicated but once you understand its use then it is often just injecting or measuring something with an item that is known.


--- Quote from: RandallMcRee on August 02, 2021, 08:53:56 pm ---You've stepped into it. If I was the customer I would now expect that you would confirm the main specs given in the data sheet:
The pre-amplifier has gain calibrated from 1mV to 1V for full scale output, and features high stability and linearity,
good CMRR and wide dynamic range.
and
Linearity <0.02% deviation.
Accuracy ±0.25%.
Stability 0.02% - 12 months.
also noise, and a few other things.
Maybe set some expectations between you, the customer and your management ??  ::)

--- End quote ---

Thankfully it was a fairly easy task. Spoke to the customer, he went "ah yeah we didn't do them last time. Don't worry we just use the CAL switch on the unit to check that the signal is getting to the scope". So I got out of that with some ease. I did have to sit down with them and explain about doing Self Cal thing on the scopes they have because many of them hadn't done a Signal Path check since 2010, and the test lab there wobbles all over the place with temps. It did clean up a few of the signals as one was a little sqiffy on the square waves. Don't worry it is not like it was a high-end test facility for a very prestigious Uni in the UK, they aren't even 9001 they are just researching with a bit of commercial stuff.

Thanks for the input.

Neomys Sapiens:

--- Quote from: mendip_discovery on August 08, 2021, 04:05:34 pm ---
--- Quote from: Neomys Sapiens on August 03, 2021, 03:09:33 am ---Nope. You respectively your company can be held liable for this. You are not able to CALIBRATE those amplifiers until you know the cabration procedure and have the suitable normals and parts. This is a very different thing to a function check and even a performance check. The latter is what you could do in a normally equipped lab. You should point that out and not give in.

--- End quote ---

As the calibration engineer, it is my task to work out how to calibrate an item and then produce a procedure from that. I'm not doing adjustments, just a calibration. There are lots of items that look complicated but once you understand its use then it is often just injecting or measuring something with an item that is known.


--- Quote from: RandallMcRee on August 02, 2021, 08:53:56 pm ---You've stepped into it. If I was the customer I would now expect that you would confirm the main specs given in the data sheet:
The pre-amplifier has gain calibrated from 1mV to 1V for full scale output, and features high stability and linearity,
good CMRR and wide dynamic range.
and
Linearity <0.02% deviation.
Accuracy ±0.25%.
Stability 0.02% - 12 months.
also noise, and a few other things.
Maybe set some expectations between you, the customer and your management ??  ::)

--- End quote ---

Thankfully it was a fairly easy task. Spoke to the customer, he went "ah yeah we didn't do them last time. Don't worry we just use the CAL switch on the unit to check that the signal is getting to the scope". So I got out of that with some ease. I did have to sit down with them and explain about doing Self Cal thing on the scopes they have because many of them hadn't done a Signal Path check since 2010, and the test lab there wobbles all over the place with temps. It did clean up a few of the signals as one was a little sqiffy on the square waves. Don't worry it is not like it was a high-end test facility for a very prestigious Uni in the UK, they aren't even 9001 they are just researching with a bit of commercial stuff.

Thanks for the input.

--- End quote ---
You did not mention that you have the function of a calibration engineer. Had I known this, I would have assumed more previous knowledge and my wording would have been different. So I can assume that you can match the precision of your normals and sources to the precision required by the device under test, even if you have to improvise somewhat.

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