
Figure 3
3
CALIBRATION
The Remote Cal Module connects directly to the MK-2 sensor via
a four conductor shielded cable. See Figure 2. Recommended
cable type is Belden 9534 or equivalent. Remove power from the
MK-2 which will connect to the Remote Cal Module. The cable
may be routed through the same conduit as other MK-2 control
wires. Located on the Remote Cal Module is a four-position con-
nector which can be deplugged to simplify wire insertion.
Interconnect the "+D", "-D", "+S" and "-S" on the module to the
respective terminals in the sensor. Note that the sensor's termi-
nal block is not depluggable but its labeling is identical to that of
the Remote Cal Module. Complete the installation by connecting
the shield's drain wire to earth ground at the sensor end only.
The operation of the primary functions on the Remote Cal
Module (i.e. calibration, sensitivity, test and associated indica-
tors) is identical to the operation of those found on the MK-2 RF
Capacitance Sensor. Activation of the module's functions affect
the sensor the same as if the push-button was pressed on the
sensor itself. Status indicators on the module will emulate those
on the sensor. See Figure 3.
Calibration
The calibration of the unit is executed with the push-button des-
ignated "CAL". The purpose of the calibration is to null out or
ignore any initial capacitance due to vessel configuration or
extreme material build up on the probe and shield. When prop-
erly calibrate, the green "CAL" indicator will be illuminated. To
initiate the calibration of the unit, first ensure that the probe is not
submerged in product. Then press and release the "CAL" but-
ton. The "CAL" indicator will flash for a short period. If proper
calibration occurs, the flashing will be followed by a continuous-
ly lit "CAL" indicator. The procedure can be done at anytime after
installation providing the material level has not reached the probe
in order to null out extreme conductive build-up or changes in the
configuration of the probe or vessel.
Sensitivity
The sensitivity of the unit relates the amount of capacitance (in
excess of the calibration value) required to place the sensor into
the detect mode (product sensed). There are four sensitivity set-
tings, "1" being the most sensitive, and "4" being the least sensi-
tive. Therefore, materials with lower dielectric constants will
require the unit to be set to a lower numbered sensitivity setting
for maximum sensing capacity. Materials with higher dielectric
constants can be set to a higher numbered sensitivity setting, so
to provide an additional amount of build-up immunity. See Figure
4 for recommended settings. The sensitivity selection of the sen-
sor is incremented by pressing and releasing the "SEN" push-
button. The existing sensitivity setting of the MK-2 sensor is
shown by the sensitivity indicators. If the unit does not sense
product when the probe is covered with material, choose a lower
numbered sensitivity setting. Conversely, if the sensor tends to
false sense (sensing when the probe is not covered with prod-
uct), increment to a higher numbered sensitivity setting.
Figure 4
SENSITIVITY SETTING OF THE MK-2
SENSITIVITY
SETTING
1
2
3
4
DETECTION
CAPACITANCE
0.5pf
2.6pf
8.3pf
18.0pf
MATERIAL
DIELECTRIC
1.5 - 2.0
2.0 - 4.0
4.0 - 7.0
> 7.0
TYPICAL
APPLICATIONS
PLASTICS, SOAP
, CEMENT
SAND, RUBBER, OILS, COAL
GRAINS, FERTILIZERS, FEED
WASTEWATER, SLURRIES, ANY
WATER BASED SOLUTIONS
Test Function
When initiated, the test function checks the MK-2 sensor's oper-
ation by effectively placing a capacitance value on the probe in
accordance with the sensitivity setting selected. Having the
capability to perform this function from the remote location is par-
ticularly important when the MK-2 is a high level sensor which is
infrequently covered with material. Performance verification pro-
vides additional assurance that the sensor remains ready to
sense product when present. To activate, first ensure that the
unit is calibrated properly indicated by an illuminated "CAL" indi-
cator, and that the probe is not submerged in product. Next,
press and hold the "TST" push-button. Proper operation of the
MK-2 is indicated by illumination of the "DET" indicator. If the
"TST" push-button is continuously pressed longer than the time
delay setting (adjustable on sensor only) the "OPR" indicator will
be activated as well. (Note: The relay contacts at the sensor will
change states whenever the "OPR" indicator status changes. Be
sure the application can tolerate a temporary change in the out-
put prior to activating the test function.) Improper operation is
indicated by the failure of the "DET" indicator to illuminate.
Lockout
In some applications, it may be desirable to restrict access to the
calibration and sensitivity functions after initial MK-2 setup. A
lockout feature is provided on the module PCB which will disable
the Remote Cal Module's "CAL" and "SEN" push-buttons. Select
the desired mode by positioning the slide switch in at either "ON"
(lockout activated) or "OFF" (lockout deactivated) as designated
on the PCB. When lockout is activated, the "LOCKOUT" indica-
tor will illuminate. Note that the test function "TST" push-button
will remain active at all times so verification of operation can still
be made as desired.
Communication Error
In the even of a communication error between the Remote Cal
Module and MK-2 sensor, a visual "error message" will be dis-
played on the Remote Cal Modules sensitivity LEDs. For one
second, the four LEDs will sequentially flash on and off indicating
a communications error. If this occurs repeatedly, see "trou-
bleshooting" section of this bulletin.