Kurz Instruments Inc. December 13, 2007
360210-AH Rev.A 504/534FTB Installation AH - 12
There is no means of disconnecting power for this unit. You will need a disconnect per
your local electrical code.
Analog Output
Loop powered wiring: The 4-20 mA linear output is a loop powered isolated signal.
The positive output terminal is diode protected against reverse voltage. The principle
wiring diagrams for these are 342038 and 342039.
Self powered wiring: The output may be self-powered in the non-isolated
mode by
jumpering +24 VDC to one of the two + 4-20 mA terminals. Then the 4-20 mA output
would be taken from the 4-20 mA negative terminal to ground. A simplified AO wiring
drawing or this mode of operation is shown in diagram 342045
. To use it in the non-
isolated mode, the receiving current should be sensed with an isolated input to avoid
ground loop currents.
AO capabilities: The 4-20 mA circuit has an 11 VDC compliance at the full 20 mA
current. So, on a 24 VDC 4-20 mA circuit, at least 11 VDC will be dropped across the 4-
20 mA output, the balance on the load resistor and wiring. For example, with a 250 ohm
load, at 20 mA the voltage drop will be 5 V on the load resistor, 19 V across the 4-20 mA
output or AO terminals. With higher voltage supplies, you have correspondingly higher
load resistance available. As a loop-powered 4-20 mA output and a 24 VDC power
supply, you can drive 600 Ω and still support the 21 mA NE-43 alarm. Do not exceed 36
VDC on the loop-powered interface or you may have leakage current from the protective
MOVs causing an error in the measurement. In summary, a loop-powered configuration
places a customer provided DC power source, the MFT B-Series output and load
resistance(s) all in series.
NE-43 alarm support on the 4-20 mA signal is also provided. This means normal
operation is clipped between 3.8 and 20.5 mA. Meter faults or sensor kickout are
indicated with either a low or high alarm on the 4-20 mA output. See the diagnostic
section for more information.
Alarms
The two optically coupled solid state relays (SSR), may be used for just about any flow
logic you can think of, sensor error output, or totalizer mode pulses. Each SSR is rated
for 0.5 A, 24 V AC/DC. As with the other I/O terminals, there are 48 V MOVs for surge
protection on this device. You must not exceed 36 V to ground or you will cause leakage
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