Many digital panel meters include electro-mechanical relay outputs to control external devices. Protecting relay contacts from excessive voltage and current is important to achieving the long operating life that digital instrumentation is designed to provide. (more…)
Many digital meters provide relay outputs to activate external alarms or controls. Two parameters, setpoint and hysteresis, are used to configure these outputs. The setpoint is a predetermined level, within the range of the meter, where a protective or control action is initiated. (more…)
The digital multimeter is one of the most widely used test instruments. A handheld DMM typically has 3½ or 4½ digit resolution and at least 3, but sometimes more than 10 functions (DCV, ACV, Ω, DCA, ACA, Hz, duty cycle, capacitance, continuity, diode test, etc).
A meter relay is a meter with a switched output that can be used to control a process or activate an alarm. In its simplest form, an analog meter relay uses mechanical contacts or a microswitch to operate an external device when the analog meter pointer reaches the level of the set pointer. Today’s analog meter relay has solid-state circuitry and a relay in place of a mechanical switch. (more…)
When Weschler started in 1941, panel meters were hand-made analog instruments. The typical meter had either a metal or bakelite case, a glass lens and an electro-mechanical movement. There were many US manufacturers during the 1940s and 1950s, including Triplett, Simpson, Weston, GE, Westinghouse, Beede, Hoyt, Hickok, Jewell, Marion, Supreme, and EMICO. Meters for DCV, DCA, ACV, ACA, and line frequency were standard.