Xycom XVME-500, Manual

Page: 35 / 104

XVME-500/590 Manual
February, 1988
4)
Use a sharp tool (knife, X-acto blade, etc) to sever the trace, as shown
in Figure 2-4 (or Figure 2-4A for the XVME-590).
5)
Use the following formula to calculate the values of ‘Rl0’ and
‘R13’:
Rg = 40K / G -
1
G = desired gain (any number between 1 and 1000)
Example: Determining adjustment to R13 necessary to get a gain of 8.
By using the formula, and assigning ‘G’ the desired value of
‘8’ , Rg is calculated to be 5714 ohms:
G = 8 Rl0 = 5.1K (standard value) R13 = 1K (adjusted to 614 ohms)
Rg
=
(40K / 8 - 1) = (40,000 / 7) = 5714
Rg is also equal to the sum of values ‘Rl0’ and ‘R13’ (Rl0 + R13). The
standard value of ‘Rl0’ is 5.1K, and that of ‘R13’ is 1K. Because the sum
of these to standard values is 6.1K (6100), ‘R13’ must be adjusted from
1K to 614K (614) to achieve the desired value.
NOTE
The resistor used should be type RN-55E, with a
temperature coefficient of 25/ppm/Degree C, max.
6) The resistor ‘RI0’ should be soldered in the position designated by the
silkscreen (see Figure 2-4 or Figure 2-4A).
7)
Potentiometer ‘R13’ can be either a BECKMAN (Model 66W) or an
ALLEN-BRADLEY (Model 85W). Carefully solder the potentiometer on the
PCB as shown in Figure 2-1A or Figure 2-2A (Note the reference to the
adjustment screw in that figure).
8)
Remove jumpers J6, J8 and J9 (if any are in place).
9) Install jumper J7.
10) Re-install the module in the cardcage and perform the input calibration
procedure (outlined in Chapter 4, Section 4.2).
11) Once the module is calibrated, the gain may be fine-tuned by monitoring
the voltage at TPl (a ground) and TP2 with a DVM, while adjusting
potentiometer ‘R13’.
2-18
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