TROUBLESHOOTING MT86/MT86HT Flow Meter
26 Fluid Components International LLC
Calibration Verification Procedure (Using Decade Boxes)
All MT86 flow meters have 1000 ohm RTD sensing points.
All MT86HT flow meters (high temperature flow elements) have 100 ohm RTD sensing points. Determine which
MT86 model type is present and use the ohm value that corresponds to the model type.
Verify each sensing point one at a time. Select the manual operation mode of the flow transmitter by closing switch SW1-3. When the flow
meter is in the manual mode, the flow transmitter monitors only the sensing point that the head-select switch SW2 selects.
Refer to the Delta "R" table for:
1. Delta "R" value in ohms
2. VDC across 250 ohms
3. Milliamp output signal values
4. Raw signal (un-linearized)
5. 0-10 VDC analog output signal
6. Display flow rate reading (in customer units) for each signal
Apply the recorded Delta "R" input values to the selected input terminal on the input board. Having the correct data sheet for the correct
input terminal is important.
Procedure
If an FC81 Field Calibrator is used, then go to the verification with a field calibrator procedure.
1. Turn OFF the power to the instrument. Disconnect the flow element cable from the input board terminal block TS1.
2. Connect two decade boxes or one decade box and a fixed resistor to terminal block TS1 (or TS2 as applicable) on the input board as
shown in the diagram of Figure 13.
3. Connect the positive lead of the DMM to the jumper J8 or to test point TP13 located at the bottom of the control board. Connect the
negative lead to the signal ground TP5(-). This readout is the analog signal, 0-10 VDC, that is before the span and zero activation
circuitry.
4. Close switch SW1-3 that puts the flow transmitter in the manual mode; this enables the head-select switch SW2 to select and monitor
one sensing point.
5. Verify that switch SW4 near the bottom of the control board is in the OP (OPerate) position.
6. Set the head-select switch SW2 to position number one; this selects the terminal block TS1 input where the decade boxes are
connected.
7. Set the decade box for the reference sensing point to 1000.00 ohms (100.00 ohms for HT).
8. Refer to the Delta "R" data sheet and set the decade box for the active sensing point to 1000.00 ohms (100.00 ohms for HT) plus the
recorded Delta "R" resistance value for each sensing point that is designated by SN - #.
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