RDP DR7AC - DR7 AC Controls and Adjustments; Voltage and Current Output Configuration; Coarse Gain Selection Method; Fine Gain Adjustment

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3. CONTROLS
(For locations, see Figure 2)
3.1 Voltage/Current Output
Voltage output is available between pins 9 & 10 (common). Current output is available
between pins 12 and 11 (common). Pins 10 and 11 are internally connected.
3.2 Coarse Gain Selection
Typically, transducer manufacturers' data sheets or calibration certificates will give a figure
allowing the full-scale output to be calculated. Possible formats for this are as follows; the
examples assume a transducer range of ±50mm.
Sensitivity format
Explanation
To convert to F.S. output
mV/V/mm
e.g. 46mV/V/mm
Millivolts of output, per volt of
excitation, per mm of travel
Sensitivity x 1 x range in mm
e.g. 0.046 x 1 x 50 = 2.3V
V/V at full-scale,
e.g. 2.3 V//V
Volt of output, per volt of
excitation, at full-scale
Sensitivity x 1
e.g. 2.3 x 1 = 2.3V
mV/mm at a specified
excitation voltage.
E.g. 230mV/mm at 5V exc.
Millivolts of output, per mm of
travel, given a specified
excitation voltage.
(Sensitivity / specified excitation
voltage) x 1 x range in mm
e.g. (0.230/5) x 1 x 50=2.3V
The standard excitation of the DR7AC is 1V, as used in the calculations above.
The following table shows the band of transducer full-scale output voltages appropriate to
each of the 8 Gain Range Settings. For example, a transducer with a full-scale output of
2.3V would be correctly set as gain range 3.
An 4-way toggle switch, SW1, sets the overall gain in the ranges shown below:
SW1
toggles
ON
Gain
Range
Gain Range
(Approximate)
Recommended Input
For ±5V O/P
For 4-20mA O/P
For ±10V O/P
1
1
X0.07 to 0.25
4V max
4V max
4V max
1+2
2
0.25 to 0.7
4V max
4V max
4V max
1+3
3
0.7 to 2.5
2-4V max
1.7-4V max
4V max
1+4
4
2 to 6
0.8-2.5
0.7-2
1.6-4V max
NONE
5
5 to 20
0.3-1
0.22-0.8
0.6-2
2
6
17 to 50
0.1-0.3
0.07-0.25
0.2-0.6
3
7
50 to 170
0.03-0.1
0.02-0.08
0.06-0.2
4
8
170 to 500
0.01-0.03
-
0.02-0.06
3.3 Fine Gain (On front panel, labelled GAIN)
A screwdriver-adjusted, 25-turn potentiometer providing a 4:1 adjustment of gain,
interpolating between the ranges set by the GAIN RANGE switch.
3.4 Coarse Zero
A 5-way toggle switch, SW2, (toggle 6 – see section 3.5) provides output zero shifts of
about 1V per step (with Fine Gain at minimum – up to 4V at maximum). When used with
FINE ZERO will suppress any output (up to 5V) to zero. All toggles OFF is normal, ie no
suppression applied. Switching toggle 1 ON with toggles 3, 4 or 5 will suppress positive
outputs. Switching toggle 2 ON with toggles 3, 4 or 5 will suppress negative outputs. The
suppression increases when toggles 3, 4 or 5 are switched ON.