What is pressure calibration by automation?

What is pressure calibration by automation?

Well that’s an interesting point, basically it means hand-free calibration. So no manipulation of weights, masses, pumping or turning a handle on a comparator. Full automation is where a computer (with correct software) controls the reference device to generate the pressure and then collects pressure readings from the device under test. This only works where you can communicate with the item under test. You can do semi automation by the software setting the required pressure and the technician taking a reading and then entering it into the computer. So with semi-automation you get some of the benefits but not all.

We see a lot of automation with electrical and temperature calibration equipment but not a lot in pressure calibration equipment. Personally I think this is driven by the dead weight tester legacy (which are fully manual) compared to electrical calibrators which have been around for 25 + years.

Pressure automation is very big in the pressure transmitter manufacturing market, with companies like Rosemount/Yokogawa having hundreds of pressure controllers calibrating thousands of pressure transmitters each day. So here automation is the way. However when it comes to the calibration of equipment used to calibrate these transmitters in the field, then very few manufactures have allowed for their equipment to be calibrated automatically i.e resistant to providing communication software or even the commands to take the readings.

Some companies make getting the pressure reading from their calibrators easy. Early Druck units and all Crystal products use a simple query based code like ?PRE to get the pressure reading. But with Beamex we need pages of macro code written just to get a pressure reading. Even the new Druck DPI 620, we can’t do automatic calibration yet!.

But what does that mean – so what if your calibration supplier can’t get the pressure reading. It takes longer and they we get less information. What we have found at CPS over the last few years, is it puts your equipment through a more thorough and in-depth calibration, i.e what happens to the unit after 20 minutes of pressure, what about those cold mornings (now that’s another blog – temperature effect). With automation you can do more pressure points up and down scale more times, which gives you a far better understanding of what your calibrator does when you are using it – as really isn’t that what its all about. Not much good having a unit that exceeds its specifications in the lab or on your bench but take it out onsite and the inaccuracy doubles because its snowing outside. Then how do you undertake calibrations with confidence.

At CPS, an automation calibration takes 2-3 hours per calibration, so your equipment is going through a very rugged calibration – not just apply a pressure and take a single reading and move on – we take up to 5000 pressure readings per calibration, hundreds at each point. It’s like taking your car for a service but then they take it for a drive from Picton to Christchurch via the Molesworth station just to make sure it will handle everything you can throw at it.

Automation also allows us to up grade the accuracy of your gauge or instrument. We do a lot of XP2i’s at 0.06% of reading accuracy. It’s easy to run a test at 0.1%, then trim the gauge (which is unlikely for a XP2i – as they meet that spec anyway from the factory), then redo the test at 0.06% accuracy. Check out one of our cal reports here and if you see a benefit in getting CPS to calibrate your calibrator then do contact us!

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