Cleveland Motion Controls DIN Rail Amplifier MWI-13261 Ultra Series Isolated REV BA - Manual (Page 21)

MAN-13261 R EV BA DIN R AIL A MPLIFIER , MWI-13261 U LTRA
3.1.2 P OWER A PPLICATION
Apply DC power to the amplifier and use a DC voltmeter to confirm that the supply polarity and voltage is within
the prescribed limits. As soon as is practical, confirm that the excitation voltage is either 5.0 VDC or 10.0 VDC as
appropriate for the type of load cells being used. Promptly identifying any over-voltage condition can help minimize
potential damage to the strain gage elements internal to the transducer. Note that the excitation voltage may rise to
approximately 6.5 VDC if the amplifier is operated without any transducers attached. This voltage will return to the
precisely regulated value when the transducer load is connected.
3.2 T
RANSDUCER
P
OLARITY
C
HECK
This step is important in identifying transducer or wiring problems early in the setup procedure. Information learned
in this check will be instrumental in setting the optimum gains for the Left and Right Instrumentation Amplifier
stages. The following steps described the polarity check only for the Left Channel (LCH), but the steps are
applicable to the Right Channel (RCH) as well.
1. Measure the -LCH load cell signal with a digital volt meter (DVM) at the input to the amplifier with respect
to the Excitation Return (EXC RET) to confirm that it is roughly 58% of the excitation voltage.
Measure the +LCH signal to confirm that it is roughly 58% of the excitation voltage.
If both measurements are less than 50% of the excitation voltage, then it is likely that the BLU and BRN
transducer cable leads have been mis-wired.
2. Measure the voltage at the +LCH input to confirm that it becomes more positive when a small trial force is
applied in the transducer’s intended force direction. The –LCH input should become less positive when the
same force is again applied. If the “sense” of this voltage change is incorrect for the way the transducer is
mounted, interchange the load cells wiring for –LCH and +LCH signals.
3. Without a calibration force applied to the load cells, measure the “UNLOADED” DC voltage difference
between the LCH+ and –LCH signals. Use the lowest practical voltmeter scale to provide a meaningful
measurement. Remember or record this measured value for later use.
4. Apply the intended full scale force to the load cell and measure the “LOADED” voltage.
Both of these voltages, as well as the difference between these two voltages, help to indicate the best Gain
setting configuration at the first amplification stage. Select the highest possible gain for the first stage that
does not result in saturation (“clipping”) of the transducer signal. If the voltages do not exceed 180mV,
then a gain of 25 is appropriate. Similarly, a lower signal of 35mV could use a higher gain of 125.
5. Set the IA gains using the jumper switches (refer to section 2.9). We recommend using the same gain
setting for both the LCH and RCH, consistent with the requirement of avoiding saturation.
3.3 C
ALIBRATION
The following sections describe the calibration process for establishing particular voltages at the +/- 10V analog
output. If you intend to use the 4-20 mA output, then make that output the focus of your calibration efforts.
Similarly, calibrate to the meter output if that is your primary focus.
P AGE 21 OF 30