Appendix 6: External Interface Modules, Rev. 1.1
A6.1.3.6 High Impedance Settings
If switches S2 to S5 are closed (on), and switches S6 to S9 are open (off), the input impedances
will be very high (approximately 3.3M Ohms), however in this mode it can only measure +/- 5V or
0-5V. These switches do not have to be made collectively. Channel A may be set for high
impedance. Channel B may be set for +/-10V (low impedance).
NOTE! The source equipment is to be checked to ensure the analog does not affect the
source equipment during power-off on the analog. If the source equipment is affected, the
addition of a 1M Ohm resister added in series to the input of the channel will increase the
input impedance, thus reducing the likelihood of affecting the source equipment.
To measure beyond the 5V range with the high impedance setting, an external voltage divider
with high resistance values is necessary. For example, to measure +/- 30V on channels A1 and
A2 with a 1M ohm input impedance, close (Turn On) S5, open (Turn Off) S9, and close SW2(1)
(these changes set the analog channel for +/-5V); place an 850K resistor in series with the input
channel, and a 150K resistor between the input channel and the common. Such changes should
only be instituted if the voltage is above 5V.
In order to support voltage and current ranges below the specifications given above, additional
amplifying isolators may need to be incorporated into the interfacing plan. Please contact Rutter
Technologies’ Product Support Department for further information on obtaining applicable
amplifying isolators.
VDR-100G3/G3S Installation Manual 06/10/2008
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