UNIT C, 4TH DIMENSION, FOURTH AVENUE, LETCHWORTH, HERTS, SG6 2TD UK
Phone: 0044 (0) 1462 672005, • E-mail:
TB-7564
Page 1 of 2
© 2014 Vermason
ZVM LIMIT COMPARATOR
Operating Instructions
1. The purpose of the ZVM Limit Comparator is to verify the
calibration of the 222755 Zero Volt Monitor by checking
four operator conditions: FAIL LOW, PASS (low limit),
PASS (high limit), and FAIL HIGH.
2. There are 10 resistor settings on the Limit Comparator,
which can be set using the rotary switch. Positions 3
through 8 have installed values. Positions 1, 2, 9, and 10
can be installed by the user for one set each of custom
low and high limits. The standard settings are as follows:
POSITION:
1.) optional low limit fail low
2.) optional low limit pass
------------------------------
3.) 1.91 Megohms FAIL LOW
4.) 1.91 Megohms PASS (ZVM default settings)
5.) 10 Megohms PASS
6.) 10 Megohms FAIL HIGH
------------------------------
7.) 35 Megohms PASS
8.) 35 Megohms FAIL HIGH
9.) optional high limit pass safe
10.) optional high limit fail high
PLEASE NOTE THAT THE ZERO VOLT MONITOR
OPERATOR LIMIT COMPARATOR IS USED TO
CHECK ONE OPERATOR AT A TIME
3. Ensure that the Zero Volt Monitor to be checked is
set up as described in the operating instructions and
has power.
4. Connect the plug from the limit comparator into the
OPERATOR 1 remote jack.
January 2014
Figure 1. Vermason
Made in the
United States of America
TECHNICAL BULLETIN TB-7564
5. Turn the rotary knob on the Limit Comparator to “x
Ohms LOW” (select x = 1.91 Megohms or the
optional low limit fail low, according to what operator
low limit the Zero Volt Monitor is calibrated).
Observe the operator 1 LED display on the front of
the Zero Volt Monitor. The yellow LED should be on
and the audible alarm should sound, indicating the
fail low condition.
6. Turn the rotary knob on the Limit Comparator to “x
Ohms PASS” (select x = 1.91 Megohms or the
optional low limit pass safe, according to what
operator low limit the Zero Volt Monitor is calibrated).
The green LED on the Zero Volt Monitor operator 1
display should be on, indicating the low limit pass
safe condition.
7. Turn the rotary knob on the Limit Comparator to “x
Ohms PASS” (select x = 10 Megohms, 35 Megohms
or the optional high limit pass safe, according to
what operator high limit the Zero Volt Monitor is
calibrated). The green LED on the Zero Volt Monitor
operator 1 display should be on, indicating the high
limit pass condition.
8. Turn the rotary knob on the Limit Comparator to “x
ohms HIGH” (select x = 10 Megohms, 35 Megohms
or optional high limit fail high, according to what
operator high limit the Zero Volt Monitor or is
calibrated). The red LED on the Zero Volt Monitor
operator 1 display should be on and the audible
alarm should sound, indicating the fail high condition.
9. Disconnect the Limit Comparator plug from the
operator 1 remote jack. Plug the Limit Comparator
plug into the operator 2 remote jack and repeat the
four tests in steps 5 through 8 to test operator 2.
10. The correct color LEDs must light for each step for
the Zero Volt Monitor to completely pass the
calibration check. If an incorrect LED comes on
during any portion of the test (example: expecting
the green LED to light in step 7 but the Zero Volt
Monitor red LED is on) recalibrate the Zero Volt
Monitor and test each operator again with the Zero
Volt Monitor cal limit comparator.
INSTALLING OPTIONAL LOW AND HIGH LIMIT
RESISTANCES
A.) Use a hex wrench to remove the rotary switch
knob. Unscrew the 2 screws on the back of the unit
and disassemble the unit.
B.) Two resistances must be installed for each
limit: one for PASS and another for FAIL. These
two resistances should be ±10% of the calibrating
resistance. For example:
