Cleveland Motion Controls Classic Series DIN Rail Amplifier Non-Isolated MWI-13466 REV CA - Manual (Page 12)

C LASSIC S ERIES N ON -I SOLATED A MPLIFIER MAN-13466 R EV CA
P AGE 12 OF 26
2.6 P OTENTIOMETERS
In addition to the Gain and Zero adjustable Potentiometers visible on the front of the unit, there is an adjustment you
can make by removing the snap-off cover on the side of the amplifier. The adjustment is on the input printed circuit
board as shown in Figure 4. The following table provides you with a list of all the Potentiometers, where they are
located on the Classic Series DIN Rail input printed circuit board, and a description of their functions. To adjust
potentiometers, refer to Adjustment Tools 3.7.
Potentiometer
Reference
Designator
Location Function
GAIN P2 Unit Front
Provides 10:1 “vernier” adjustment of the variable gain amplifier. It is a
multi-turn potentiometer, with clockwise rotation causing an increase in
amplifier gain. When turned fully counter clockwise, the potentiometer will
cause the amplifier stage to provide the minimum gain of 1.8.
ZERO P1 Unit Front
Provides a fine zero (offset) adjustment. It is a multi-turn potentiometer,
with clockwise rotation causing a positive shift in the analog outputs. It
should be set mid-way prior to setting the COARSE ZERO adjustment.
Coarse Zero P5
Input, behind
access cover
Establishes the coarse zero of instrumentation amplifier. Because of the
ability to cause +/- Full scale (+/- F.S.) output shifts, it is important to
correctly follow the final set-up and calibration procedure so that premature
amplifier “clipping” is avoided
2.7 E XCITATION V OLTAGE S ELECT
The Excitation Voltage is determined by the position of jumper switch J3. Refer to Figure 4 for Jumper-switch
locations. The jumper default setting is J3 (1-2) for 5.00V excitation Do not use 10V setting J3 (2-3) unless
explicitly permitted by the load cell electrical specifications. Promptly verify the excitation voltage after power-up
to avoid overdriving strain gages. Note that if there is no external load resistance, the voltage may rise to 6.4V, but
will immediately regulate at 5.00V when the load cells are connected.
Keep in mind that the strain gage based load cells can readily operate at less than rated voltage (with a
corresponding reduction in output signal). This fact is helpful in the event that a “10 V “ load cell exhibits an output
signal that is excessive for even the lowest amplifier gain.
2.8 G AIN S ELECT S WITCHES
The group of jumper-switches that control the fixed gain of the Instrumentation Amplifier (IA) are located closest to
the front left edge of the Input card. (Refer to Figure 4) The lowest gain (Av = 5) occurs when all of the switches
are in the 1-2 position. As switches are moved “away” (into position 2-3) from left to right, the gain progressively
increases as described in following table:
Jumper Switches
J10 J9 J7
Voltage Gain
1-2 1-2 1-2 5
2-3 1-2 1-2 25
2-3 2-3 1-2 125
2-3 2-3 2-3 620
When changing the internal Jumper-switch settings, it is always advisable to change the settings
with the 24 VDC power removed. If this is not possible, it becomes particularly important to use
a non-conductive tool to alter switch positions.
Make sure that Jumper- switch settings are fully in position to avoid accidentally leaving a switch
in an “in-between” state.
The total gain range of the amplifier is the product of the IA and variable amplifier gains
(variable).
Using the lowest gain switch settings, the net gain is 5 x (1.8 to 18) or 9 to 90
With the other gain combinations available, a 10 volt output can be produced with input voltages
ranging from between 0.002 to 0.50 volts.