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Zeroing of pressure instruments

Adjusting the zero point is important when high accuracy is required.

The zero point signal of a pressure transmitter can shift:

  • when it is installed, because of the mounting position or mechanical strain on the pressure connection,
  • in operation, because of temperature changes,
  • over a long time, because of aging.

Long-term stability (the maximum signal drift per year) is a quality parameter which must be specified in the data sheets.


When, how often?
If high accuracy is required, JUMO recommends

  • adjusting the zero offset signal during commissioning, after the instrument has been installed
  • and subsequently according to requirements (e.g. every 12 months).

For certain installations, such as in power plants, regulations demand a documented check of the zero offset signal.

Which instruments?
Zero offset adjustment is only possible on the more sophisticated instruments:

JUMO dTRANS p02 series:                               digital, via keypad or the HART interface
JUMO CANtrans series:                                     digital, via CAN interface
JUMO dTRANS p30 series:                               analog, by potientiometer
JUMO MIDAS series:                                           no zero adjustment possible

What is the zero point?
for absolute pressure:                                        absolute vacuum (0 bar absolute)
for relative pressure:                                           atmospheric pressure (0 bar relative)
for differential pressure:                                     both pressures are equal

Multi-way valves for easy zero point adjustment

The use of a multi-way (manifold) valve enables test and adjustment in normal operation, i.e. on site, without any dismantling:

for absolute pressure:                                        2-way valve (for connection to a vacuum pump)
for relative pressure:                                           2-way valve (open to theatmopheric pressure)
for differential pressure:                                     3-way or 5-way valve

pressure_t1q5 pressure_t1q5_4 pressure_t1q5_2