Aalborg DFM Digital - Manual (Page 41)

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7.3.7 Gas pressure 4-20 mA analog output
calibration (DFM 27/37/47)
1. Install jumpers J4 on the analog PC board for 4-20 mA output (see Table VI).
2.
Connect a certified high sensitivity multi-meter set for the current
measurement to the pins 4 (+) and 17 (-) of the 25 pin D connector.
3. Write 4000 counts to the DAC channel 3: !11,WRITE,3,4000[CR]
4. Read current with the meter and calculate:
5. Write zero counts to the DAC channel 3: !11,WRITE,3,0CR]
6. Read offset current with the meter and calculate:
7. Save PresOutScale_mA in to the EEPROM: !11,MW,33,Y[CR]
Save PresOutOffset_mA in to the EEPROM: !11,MW,34,Z[CR]
Where: Y - the calculated PresOutScale_mA value.
Z - the calculated PresOutOffset_mA value.
Note: When done with the analog output calibration make sure the DAC
update is enabled and the BackDoor is closed (see command below).
Enable DAC update by typing: !11,WRITE,4,N[CR]
Unit will respond with: !11,DisableUpdate: N
Close Backdoor mode by typing: !11,MW,1000,0[CR]
Unit will respond with: !11,BackDoorEnabled: N
7.4 Temperature or/and Pressure sensor
Calibration
Calibration of the temperature and pressure sensors for DFM 27/37/47 devices is
not described in this manual. Temperature or/and pressure sensors re-calibration
requires factory assistance.
8. RS-485/RS-232 SOFTWARE INTERFACE
COMMANDS
8.1 General
The standard DFM comes with an RS-485 interface. For the optional RS-232 inter-
face the start character (!) and two hexadecimal characters for the address have
to be omitted. The protocol described below allows for communications with the
,