Cleveland Motion Controls Classic Series DIN Rail Amplifier with Isolated Output MWI-13467 REV CA - Manual (Page 21)

MAN-13467 R EV CA C LASSIC S ERIES A MPLIFIER W / I SOLATED O UTPUTS
Page 21 of 30
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 on in the setup procedure. Information
learned in this check will be instrumental in setting the optimum gains for the Instrumentation Amplifier stage.
1. Measure the -INPUT signal from transducer 1 with a digital voltmeter (DVM) at the input to the amplifier
with respect to the Excitation Return (EXC RET) to confirm that it is roughly 50% of the excitation
voltage.
Measure the +INPUT signal from transducer 2 to confirm that it is roughly 50% of the excitation voltage.
If either measurement is less than 45% or greater than 55% of the excitation voltage, then it is likely that
the transducer cable leads have been mis-wired.
2. Measure the voltage at the +INPUT to confirm that it becomes more positive when a small trial force is
applied in the transducer’s intended force direction. The –INPUT signal should become less positive when
the same force is again applied. If the “sense” of both of these voltages change is incorrect for the way
the transducer is mounted, interchange the load cells wiring for the –INPUT and +INPUT signals. If only a
single transducer exhibits the incorrect “sense, interchange the excitation and excitation return leads on
that particular transducer.
3. Without a calibration force applied to the load cells, measure the “UNLOADED” DC voltage difference
between the +INPUT and –INPUT 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 gain using the Jumper-Switches (refer to section 0).