Kurz Instruments Inc. December 13, 2007
360210-AH Rev.A 504/534FTB Installation AH - 10
Do not use Liquid tight Flex conduit for 5-wire sensor connections, shielding is not
effective.
Typical Hook-Up Wiring Diagrams
For both the AC & DC powered versions of the MFT B-Series, typical summarized wiring
diagrams for most applications are available as defined in DCN 342038. This covers the
TS and transmitter attached (TA) configurations. Examples for 4-20 mA connections and
Modbus are shown along with the terminal definitions and cable wiring notes.
For the transmitter separated (TS) enclosure configuration, the 5-wire sensor
connections must be made as shown in DCN 342039. The connection between the
enclosure groups must be shielded to maintain the CE rating.
24 VDC Powered Flow Transmitters
The 24 VDC power is a nominal voltage since all circuits have a regulated supply and will
work between 18 and 30 VDC. You may also use an unregulated power supply with 50
to 60 Hz ripple as long as the instantaneous voltage is between 18 and 30 VDC.
Surge currents during sensor warm up could require up to 1 A and will fall off after it
warms up in about 20 seconds. At no flow the current will be about 0.1 A and about 0.3
A for high flow rates (12,000 SFPM). The power is protected against reverse polarity so
if no current flows or there is no output signal you may want to check the polarity against
the wiring diagram, DCN 342038.
The flow transmitter is grounded. The 24 VDC power and 4-20 mA signal have MOVs
(metal oxide varistors) to clamp voltage spikes going into the unit. These are 56 V
nominal (voltage level at 1 mA) and do not conduct significant current below about +/- 36
VDC relative to ground. Consequently, the isolated 4-20 mA signals, alarms etc., can
not have a significant common mode or bias voltage to prevent leakage currents on the
MOVs, which can cause an error in the flow measurement if occurring on the 4-20 mA
output.
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