Watlow Electric Revision 5 - Manual (Page 29)

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capacitors can be installed for signal conditioning. Please consult
ANAFAZE. The PC board silk screen shows the resistor locations.
5.6.2 USE OF THE SHIELD CONNECTION
The shield connection provides a third input which is switched as each
channel is measured. It is the ground reference for the measurement section.
By switching this reference with every channel, the effective measurement
ground can float to match the ground at the sensor, thus greatly reducing the
error caused by different ground potentials (common mode).
The system is factory set for use with non-shielded cables. Zero ohm
resistors in the RD position connect each low input to shield. Normally
when non-shielded cables are used, this will result in the lowest noise pick-
up.
If shielded cables are used, the shield should be connected to ground or the
low signal output at the sensor if possible. If this is done, the RD resistor for
that channel must be removed.
WARNING - USE SHIELD CORRECTLY
If the shield is used for any input always remove the factory installed
RD resistor.
5.6.3 VOLTAGE INPUTS
DC Voltage inputs should be connected with the positive side to the HIGH
terminal and the negative side to the LOW terminal. The input range is -10
to +60 mv. Signals greater than 60 mv must be scaled with resistors to
match the input full scale to 60 mv. For scaling the positive input should be
connected to the AUX terminal and the negative input to the LOW terminal.
The scaling resistor RA is selected as the voltage dropping and/or current
limiting resistor. RB is selected for the 60 mv full scale dropping resistor. It
should normally be less then 300 ohms and should never be greater then
1000 ohms. Any value above 1000 ohms for RB will cause error due to the
upscale burnout circuit. Typical standard value scaling resistors are as
follows:
0-100mv 0-500mv 0-1v 0-5v 0-10v
RA= 499 ohms 5.49k 6.91k 39.2k 49.9k
RB= 750 ohms 750 ohms 442 ohms 475 ohms 301 ohms
ACC.= +.1% +.1% +.2% -.2% -.1%
Please note section 5.6.2 regarding the shield connection.
Please note section 5.8 regarding scaling and calibration.
The above values are standard metal film values and will give an accuracy
of +/- .25% when using .1% tolerance resistors.
Any possible error due to resistor tolerance may be corrected by using
scaling in ANASOFT.