Analog output overrange behavior – Vaisala HMDW80 User Manual

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User's Guide _______________________________________________________________________

16 ___________________________________________________________________ M211510EN-C

Analog Output Overrange Behavior

Analog outputs of the HMDW80 series transmitters have a defined

behavior when the values measured by the transmitter are outside the

scaled analog output range:

- Output is clipped at the end of the range.
- Output is set to error state when measured value is 5% outside the

- Output resumes normal function when measured value is back on the

scaled range.

NOTE

HMW82/83 and TMW82/83 transmitters are different from the rest of

the HMDW80 series. Their analog output is clipped at 10% outside the

scaled range, and their analog outputs enter the error state when the

measured value is 20% outside the range.

For example, consider the temperature output of the HMD82 transmitter.

The output is 4 ... 20 mA, scaled to -40 ... +60 °C (-40 ... +140 °F).

- When measured temperature rises above +60 °C (+140 °F), the output

rises to 20 mA and stops rising even if temperature rises further.

- If the temperature rises above +65 °C (+149 °F), the output enters the

error state of 3.6 mA.

NOTE

This overrange behavior does not mean there is a problem with the

measurements, and it does not affect the readings shown on the display

(if included in the transmitter model). The display always shows the

currently measured readings if the measurement is operating without

error. For more information on transmitter errors, see section Error