BO Series Current Sensing Switch

Current Detector - Heater Burnout Detector

With Self powered Transistor(open-collector), Triac, or relay output: A Current Sensing Switch


Wiring Diagrams


Single Phase


Three Phase





Single phase

Simply thread the wire to the load through the RO series sensor and the self powered sensor activate the output when the current exceeds the set point.

Three Phase Delta

With one sensor you can monitor heater elements on all three phases. This is done by detecting current unbalance between the phases with this configuration - be very careful to follow the diagram exactly - there are 3 loops from the delta triangle - you can not thread the 3 supply lines and get the same result!

Monitoring the phase imbalance can let us detect burned out heater elements, phase supply problems that might damage motors or other equipment. The BO series sensor would activate on an imbalance that exceeds the set-point.

Three Phase 4-wire-Y

Another way of seeing the phase imbalance is the 4-wire-Y. Activates on imbalance the exceeds the set point.

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BO Series Current Sensing Switch
Set point current range (specify with order) 5 to 100A Full Scale
Set point accuracy +/-15% (5% on adjustable units) 10% dead-band
Relay Output version -RELAY
4A @ 220 Vac
TRIAC Output version -TRIAC
2A @ 220 Vac
Transistor Output version -OC
20 mA 24V (Pin 8 negative.; Pin 6 positive)
Ambient Operating Temperature 0 C to 60 C
Octal Case Size 60.7[2.39] X 44.85[1.77] X 70.75[2.79]mm[inches] (excluding octal pins)
   With module in socket - 105[4.14] mm[inch] total height
Pass through opening 22.2mm [0.875"]
 Optional 31.7mm [1.25"] -LD large diameter opening available
Adjustable versions available -ADJ
Allows a 2:1 range ( Full scale current of 10A  adjusts from 5 - 10A)
Relay contacts 5A@30Vdc/120Vac see drawing below for pin out
Relay power supply 12V or consult factory

[] - denotes legacy units

Adjustment Option

For applications that need a settable current point the adjustment option, a trim potentiometer is provided that covers a 2:1 range. ( for example 5 - 10Aac ).

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Use is confined to Engineers with more than 370 course hours of electronic engineering for theoretical studies.
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