Dynasonics MFX Series Insertion MagProbe Flow Meter - Manual (Page 19)

Rev. 01/11 -1.17- MFX
4-20 mA Output The 4-20 mA Output Module interfaces with most recording and
logging systems by transmitting an analog current signal that is
proportional to system flow rate. The 4-20 mA ISO-MOD may be
configured via jumper selections for either an internally powered
mode (current sourcing) Figure 1.11A or externally powered mode
(current sinking) Figure 1.11B.
Internal Power Configuration: Ensure that jumpers are in place at
JP1 and JP2 on the module. See Figure 1.11A. In this
configuration the 4-20 mA output is driven from a +24 Vdc source
located within the MFX flow meter. The 24 Vdc source is isolated
from DC ground and earth ground connections within the MFX
instrument. The module can accommodate loop loads up to 800
Ohms in this configuration.
External Power Configuration: Remove the two jumpers located at
JP1 and JP2 on the module. See Figure 1.7B. In this
configuration the 4-20 mA module requires power from an external
DC power supply. The voltage of the external power source must be
sufficient to power the module and drive the loop load. The loop loss
attributed to the ISO-MOD is 7 Vdc, so the minimum voltage
required to power a loop can be calculated using the following formula:
Loop voltage (min) = (loop load Ohms x 0.02) + 7
PART 1 - ISO-MOD
Figure 1.11A
Internally Powered
4-20mA
Figure 1.11B
Externally Powered
4-20mA