Wiring

Back up pump control is a critical part of any pump control application, ensuring that failure does not result in a potentially hazardous overflow or the unwanted emptying of a tank. Ideally, back up sensors work independently from the control system, so that failure of the primary controls will not disable them.

This means basic control features such as hysteresis...

Rapidly changing liquid levels can overwhelm a single pump, and cause excessive wear and tear. To prevent this, additional pumps can be added to control the liquid level.

A common example of this is a duplex lift station; liquid is pumped from a well to a higher elevation, where gravity can carry the liquid to the next station. Lift stations are used primarily in the wastewater industry, to carry liquid waste to the treatment plant.

A duplex lift station uses two pumps: a lead pump and a lag pump...

Here, the cable shield is tied to the case ground by way of the connector. Cable shielding must be connected to ground to work.

Electromagnetic Interference, or EMI, can cause problems in even sophisticated industrial control system when not properly protected. Instrumentation, such as a level sensor or a pressure transducer, can perform erratically, inaccurately, or not at all when exposed to EMI.

Simply put, EMI in an industrial setting is electrical noise that disrupts electrical circuits in instrumentation. These disruptions can range from simple signal degradation to a total loss of sensor...

Simplex pump control is a relatively simple task. A float switch with a bit of hysteresis will do just fine. There are, of course, continuous level sensors that may be advantageous under the right circumstances. However, for this article, we will focus on wiring a KA series cable suspended float switch for simplex pump control.

There are generally two approaches to grounding pressure sensors. Both work just fine, as long as they are used in isolation. However, when both are used together, problems can occur.

The first is to use a chassis, or case, ground. This means that the manufacturer has designed the transducer to make contact to earth ground through the case/housing of the sensor. This approach allows the transducer to be naturally grounded during the installation process.

The second approach is to use a...