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Decontamination Process Validation

Pressure Calibrator Guidance

Calibrating Pressure Like a Pro

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Although pressure calibration is technically a quicker and more straightforward process than temperature calibration, it can be less obvious that something is wrong while you are doing it, so it’s worth taking a look at a few simple checks to make life easier…

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Pressure calibration in TQSoft creates a straight-line relationship between the pressure reported by your pressure calibrator, and the voltage created by the pressure transducer. In other words, when TQSoft is told that the voltage created at e.g. 300mBA is 0.75 volts, and at 3000mBA is 2.5 volts, it can then translate any further voltage received into a displayed pressure.

For this reason, during calibration, TQSoft will display a voltage rather than a pressure reading at the low and high points, then switch to displaying an accurate pressure value for the checkpoint.

There are a couple of quick checks you can do to ensure your calibration is going to plan…

1. When you begin a calibration and TQSoft is waiting for stability at the low point, check the voltage being received while at atmospheric pressure before you begin using your pressure calibrator.

  • Using an Isopharm pressure transducer and power supply, this should be around 1.1-1.2 volts (this will vary slightly depending on local atmospheric pressure and variations in the electronics). Other hardware may vary, but should always be consistent.
  •  A reading of zero (to a couple of decimal places) indicates a power issue – no voltage is reaching the datalogger, so check connections throughout the system, and check the power LED on the power supply.
  •  A reading which bounces rapidly up and down, or simply increases gradually generally indicates a faulty transducer.
  •  A negative reading indicates that one of the connections has been wired back to front.
Calibration Progress

2. Because of the straight line relationship between voltage and pressure, almost all errors in calibration are going to be at one or the other ends of the scale. Once the high point has been calibrated, TQSoft immediately switches to displaying a calibrated pressure – before you lower the pressure to reach the check point.

It is therefore a useful exercise to check the pressure displayed against your pressure gauge before changing the pressure from the high point – the two should match. Once you are satisfied the high point is correct, we would recommend dropping the pressure down to atmospheric in order to check the displayed pressure in TQSoft against the pressure gauge, before pumping back up to the check point and completing the calibration

Calibration Progress 2

If you are struggling with a leak in the system, it is likely to be from one of two places

  • The pump is leaking internally – check the switch between pressure and vacuum is fully one way or the other. Many pumps also allow field servicing and replacement of the internal seals, as these can compress and fail over time
  • Isopharm pressure transducers are ¼” BSP – check the pump connection is also BSP, as some have an NST thread. BSP and NST threading is similar enough to allow you to partially screw the two fittings together but will not give a tight seal (at least not without a very liberal application of PTFE tape!)
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