Gossen MetraWatt METRACAL MC, Operating Instructions Manual

Page: 52 / 84

52 GMC-I Messtechnik GmbH
Calibration Functions: V – Hz –
Ω
– Temp – mA – mA
6.6.1 Current Sink – Simulation of a 2-Wire Transmitter
A current sink (0
…
24 mA) or current loop load can be simulated
with this function. The calibrator regulates the current, which flows
via the calibrator jacks from an external power supply,
independent of direct voltage applied to the jacks (4
…
27 V). The
calibrator varies internal resistance such that the selected current
value is maintained.
Note

The last selected simulation range is saved to memory.
Voltage at the calibrator jacks may not exceed 27 V in the
current sink operating mode, because thermal overload
would otherwise occur and the fuse would blow.
LoVolt
appears at the display if voltage is too low.
Example of a 2-Wire Transmitter Measuring Circuit
6.6.2 Current Source
Internal supply power is used to simulate a current source.
Note

The current source’s internal control loop is monitored: If
voltage drop at the external load (burden) is greater than
20 V, or if the electrical circuit is interrupted, “Hi burd”
appears at the display.
No external voltage may be applied to the calibrator jacks
in this operating mode.
The calibrator is protected against brief application of large
external voltages with a replaceable fuse in the event of
operator error (see section 10.3).
– + +
Periphery Devices
24 V
4 ... 20 mA = 0 ... 100
°
C
+
+
–
–
Power
Supply
– + +
Periphery Devices
+
–