Rh eo n i k M esst ech n i k
RE V . L O ct o b er 2014
.
RHEONIK Coriolis Flowmeter
Operation Manual RHE 07, 08, 11
Page
31
Using a digital voltmeter the voltages can be checked:
Voltage measurements
Terminal
Circuit
Voltage
Measuring points
_____________________________________________________________________
1
Drive +
0.25–7 VAC
1-2
2
Drive -
3
PT100
130 mVDC at 20 °C
3-4
4
PT100
5
PT100
130 mVDC at 20°C
3-5
6
Coil 1 +
10 - 150 mVAC
6-7
7
Coil 1 -
8
Coil 2 -
9
Coil 2 +
10 - 150 mVAC
8-9
If the values are within the above limits, the meter will oscillate normally.
If the measured voltages are not within the ranges shown in the table, disconnect the
transmitter and check the resistances at the sensor RHM terminals:
Resistance measurements
Terminal
Circuit
Resistance
*
Measuring points
_____________________________________________________________________
1
Drive +
5-70 ohms
1-2
2
Drive -
3
PT100
107-109 ohms at 20 °C
3-4
4
PT100
5
PT100
0 ohms (short circuit)
4-5
6
Coil 1 +
10-160 ohms
6-7
7
Coil 1 -
8
Coil 2 -
9
Coil 2 +
10-160 ohms
8-9
*
Resistance values are given for room temperature!
The measured values are very temperature dependent i.e.:
Pick-up coil resistor 120 ohms at 20°C, but 230 ohms at 350°C sensor temperature.
If one of these values is infinite, the sensor RHM is defective.
Insulation resistance measurements:
Check insulation resistance to earth ground (sensor RHM housing).
If a short circuit between any sensor terminal and sensor housing is measured, the sen-
sor RHM is defective.
If no problems are located at the sensor resistance, check Sensor-to-Transmitter wiring
for correct connections and for no shorts or opens, loose conductors or poorly connected
wiring.
