Frequency Meter

Line Frequency Measurements

Frequency is an important parameter for an ac waveform. The frequency, in Hertz, is defined as the number of cycles per second. It can also be expressed as 1/T, where T is the time for one cycle. One period is the duration of one complete cycle, in seconds. (more…)


Bluetooth for Instrumentation

Most of us are familiar with Bluetooth as the connection from a cell phone to wireless earbuds or a remote speaker. This low-power communication protocol is simple to set up and use. It operates in the globally unlicensed industrial, scientific and medical (ISM) band from 2.40-2.48 GHz. (more…)

4-20mA Loop

Reducing Burden in a 4-20mA Loop

Current loops are a popular method for monitoring equipment and processes in industrial environments. Some of their advantages were discussed in an earlier posting. Additional advantages of the 4-20mA loop are:
– easy detection of an open loop, since the signal zero is represented by 4mA.
– the offset zero allows use of loop-powered devices that don’t require a separate power connection. (more…)

Electrical Outlet

Ground Fault Sensing for Industrial Applications

In residential applications, ground fault sensing is used to protect a building’s occupants from electric shock. Everyone is familiar with the ground fault interrupter (GFI), incorporated into a duplex outlet, that quickly opens the circuit when a fault is detected. The National Electric Code mandates their use in kitchens, bathrooms and other wet locations. To provide a high degree of protection in these areas, the trip limit is set at 6mA by national safety standards. While operator safety is important in industrial settings, ground fault sensing is also used there, with different limits, to protect equipment from damage. (more…)


Converting a CT Output into a DC Process Signal

A question frequently posed to the Weschler Application team is: How to convert the output of an existing current transformer into a DC process signal? In North America, current transformers typically have a 5 amp secondary. (more…)