We just bought a new Testo 552 and used it for the first time today. To perform a test pull, using an almost brand new YJ Bullet vacuum pump (with fresh oil change) new Appion 1/2" vacuum hose connected directly to the the vacuum pump "tree" using Nylog, the pump would only pull down to 910 microns. Rechecked all fittings tight, you know the routine.... Decided to consult the manual.... what a novel idea!
After following the instructions for the field calibration as below, the unit would pull down to ZERO microns within 20 seconds. My question is.... does the procedure just calibrate the micron gauge to the best vacuum that the pump can pull? If so, what if the best it can do is 910 and after field calibrating it reads ZERO, are we erroneously reading a vacuum pull that is not truly the amount in comparison to other micron gauges?
I would appreciate your feedback on this quandary!
4.6 Field calibration
- Field calibration should be carried out at <15 hPa, field calibration is
not possible at ambient pressure.
- The connected vacuum pump should ideally be able to create a
minimum trace pressure of <0.1hPa.
- Field calibration tunes the testo 552 to your vacuum pump.
1 - Connect the vacuum pump to a port of the testo 552.
- Close the second port with the sealing cap.
- Start the vacuum pump.
2 - Wait until minimum pressure is reached.
- Press and at the same time for at least 3 seconds.
The testo 552 is zeroed and field calibration is completed