Vega DSGH - Measuring the Current Loop Output

42 DSGH Installation and Operation Guide
Calibration
To correlate the 4 mA ... 20 mA to the process value, set the span of the
current loop output.
A direct measurement of the current is preferable: hook the meter up in
series with the instrument and the DCS. However, if you know the
resistance of the DCS, use a voltage measurement to calculate the current.
Measuring the current loop output
Before a current loop calibration:
 Connect an ammeter or the DCS to:
• Terminal connections 13 (mA +) and 14 (mA -)
• Test points H1 and H2
• Anywhere along the current loop
 Make sure there is a 250 – 800  load on the current loop. If no load or
an insufficient load exists on the loop, it may require temporary
Note: The current loop and process spans are independent and set
separately. The current loop span sets the density indications for
the 4 mA and the 20 mA outputs. The process span sets the
endpoints of the calibration curve.
Current meter
Voltmeter
Terminal block pins
13 and 14
Detector
housing
DCS
R
t
Terminal block pins
13 and 14
Detector
housing
R
t