What does the Excitation Monitor do?

Most Hardy weight controllers have a feature called Integrated Technician (IT) that can check the individual signal millivolt output of each of your load cells or load sensors. On the HI 2151/30WC, HI 1746WS and the HI 1756WS, an additional feature called the Excitation Monitor (and is a sub-function of the IT feature) continuously monitors a systems excitation current to check for open or shorted load sensor excitation wiring or damaged or broken excitation wire(s) between the weigh module, Remote Terminal Assembly (RTA), if used, and the junction box.

At the time of calibration, your HI 2151/30WC, HI 1746WS or HI 1756WS will use the measured current draw for the load cell system and the sense voltage to calculate the load cell resistance. that controller will store this calculated value.   Then continuously monitor the current draw and sense voltage for the system and compare this new value to the stored value. If the current value deviates more than a +/-11% from the stored value, you will get an Excitation Error condition (ERRExC in the 2151/30 or module status word bit 9 is set to 1 in the HI 1746WS and HI 1756WS).

In a system with Hardy C2® load sensors, IT computes the correct current and displays alarms if the initial measured current is out of tolerance. In a system without Hardy C2® load sensors the initial current read is done at the time of the Cal Low command and becomes the reference standard, whether the initial current is right or wrong. If your measured current deviates +/- 11% from that standard you will get an ERRExC error on your Hardy Instrument.

NOTE:  If you have never calibrated the system with the current load cells, or if you change load cells on the system, you will probably get an Excitation Error until the calibration is successfully completed.