Model 1264 Powder Feeder
Operator’s Manual
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Issued: 04/16
Page 37
To calibrate the circuit to the external input:
1)
Set Jumper JP1 to position “B”
2)
Adjust potentiometer R20 fully clockwise. See Figure 4-2.
3)
Apply a current of 4 mA to J4-5 with respect to Iso Gnd (J4-10).
4)
Adjust potentiometer R17 (offset) for a voltage of 0VDC at U8 Pin 1
with respect to Iso Gnd.
5)
Apply a current of 12.5 mA to J4-5 with respect to Iso Gnd.
6)
Adjust potentiometer R18 (gain) for a powder wheel speed of 16
RPM. See Figure 4-2.
7)
Adjust potentiometer R20 for a powder wheel speed of 12.5 RPM
8)
Apply a current of 20 mA to J4-5 with respect to Iso Gnd.
9)
Adjust potentiometer R20 for a powder wheel speed of 25 RPM.
10)
R18 and R20 will interact with each other, so it will be necessary to
repeat steps 5 through 9 until the wheel speed is linear throughout its
range.
NOTE
1)
For full resolution of 4-20 mA, but to lower top wheel speed while
retaining resolution, you can decrease the value of the external
resistor. For instance, if you place a 65 ohm precision resistor in the
circuit, your top wheel speed will be roughly 12.5 RPM at 20mA.
Recalibration of the circuit will be required.
2)
It is recommended that your wheel speed reading be made using a
calibrated tachometer. Although the display on the 1264 panel is quite
accurate, it is for reference only. All calibration readings should be
made with N.I.S.T. traceable instruments to ensure accuracy.
