INSTALLATION GUIDE
H908
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opEration
The H908 is a current-sensitive switching device that monitors current (amperage) in
the conductor passing through it. A change in amperage in the monitored conductor
that crosses the switch (setpoint) threshold plus the hysteresis value will cause
the resistance of the FET status output to change state, similar to the action of a
mechanical switch. In this model, the setpoint is adjustable through the action of a
twenty (20) turn potentiometer (see the CALIBRATION section). The status output is
suitable for connection to building controllers or other appropriate data acquisition
equipment operating at up to 30 volts. The H908 requires no external power supply
to generate its output.
The H908 housing offers unprecedented mounting flexibility. The mounting bracket
can be attached in three different places. Additionally, the bracket is compatible with
the Veris AH01 DIN Rail clip, allowing DIN mounting.
notEs
troublEshooting
For load currents less than sensor minimum rating:
Wrap the monitored conductor through the center hole and around the sensor body
to produce multiple turns through the "window." This increases the current measured
by the transducer.
DANGER: 5A CTs can present hazardous voltages.
Install CTs in accordance with manufacturer's instructions.
Terminate the CT secondary before applying current.
H68xx‑5A CT
> 135A (H908 max.)
For load currents greater than sensor maximum rating:
Use a 5 Amp (H68xx series) Current Transformer (CT) as shown.
Problem Solution
No Reading at Controller • Check sensor calibration (see above)
• Check for amperage in monitored conductor (> 2.5A)
• Assure that sensor core mating surfaces are clean and
that the core clamp is completely closed
Setpoint screw has no stops The setpoint screw has a slip-clutch at both ends of its
travel to avoid damage.Twenty turns CCW will reset
the sensor to be most sensitive. Repeat calibration
above.
Both LEDs are lit Setpoint screw is too far clockwise. See solution above.
CAUTION
RISK OF EQUIPMENT DAMAGE
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calibration
A. To monitor under-current (belt loss, coupling shear, status)
1. Turn setpoint screw
clockwise until Status OPEN
LED turns ON.
2. Slowly turn the screw counter-clockwise until the Status CLOSED LED just
turns ON.
3.Turn the screw an
additional ¼ turn
counter-clockwise for
operational margin.
B. To monitor over-current (mechanical problems, seized impeller)
3. Turn the setpoint
screw an additional
¼ turn clockwise for
operational margin.
1.Turn setpoint screw
counter-clockwise until Status
CLOSED LED turns ON.
2. Slowly turn the setpoint screw clockwise until the Status OPEN LED just turns ON.
+
+
Before beginning calibration, establish normal load conditions.
Then choose either A or B below.
Controller must be
programmed to account for the
extra turns. e.g., if four turns
pass through the sensor (as
shown) the normal controller
reading must be divided by 4.
< 2.5 A (Sensor Min.)
