How to Measure Relays using a Multimeter

How to Measure Relays Using Multimeters – In a previous article has explained the working principles of Relay and its functions. In this article we will discuss about how to measure or test relays using multimeters. Basically, relay is an electromechanical component consisting of a coil, a set of contacts that make up a switch and also the connecting terminal legs. In other words, relay is an electronically operated switch. Also read:  Relay and its functions.

There are 2 Contact conditions in the Relay, namely Condition NO (Normally Open) and NC (Normally Close). Contacts that are always in the OPEN position when relay is not activated are called NO (Normally Open). While contacts that are always in a CLOSE position when relay is not activated are called  NC (Normally Close).

How to Measure Relay with Multimeter

We can use analog multimeters or digital multimeters to measure or test whether the relay we want to test is in good condition or not. The conditions measured include coil relay resistance values and contact point conditions when activated or when not activated. To be more accurate, we need a Power Supply to activate the Relay in question (e.g. 9V Battery).

Here’s how to measure relays using a digital multimeter:

Measurements on Relay Conditions are not enabled:

1. Set the position of the Multimeter Switch at ohm position (Ω)
2. Connect one of the Multimeter Probes on terminal “COM” and the other probe in Terminal NC (Normally Close), making sure the value shown on the Multimeter Display is “0” Ohm. This condition indicates between Terminal “COM” and Terminal NC is well connected (Short).
3. Move the Multimeter Probe located in Terminal NC to Terminal NO (Normally Open), making sure the value shown on the Multimeter Display is “Infinite”. This condition indicates that between Terminal “COM” and Terminal NO does not have a relationship or is in good Open condition.
4. Connect the Multimeter Probe to the Terminal Coil (2 Point) to measure whether the  Coil Resistance value matches the specification set by the Relay maker (Manufacturing specification).

Read also PTC and NTC Thermistors with Multimeters

Measurements on Relay Conditions are enabled:

1. Now enable Relay by connecting the electric current according to its Relay voltage. For example, by using a 9V battery to activate it.
2. There will be a “click” sound when the Relay is active after the electric current is drained. The “Click” sound indicates contact points have moved from nc position to no position.
3. Make sure the Multimeter Switch Position is still in ohm position (Ω)
4. Connect one of the Multimeter Probes on Terminal “COM” and the other probe in NC (Normally Close), making sure the value shown on the Display is “Infinite”.  This condition indicates that between Terminal “COM” and Terminal NC has no relationship at all at the time relay is activated or in good open condition.
5. Moving the Multimeter Probe located in Terminal NC to NO (Normally Open), make sure the value shown on the Display Multimeter is “0” Ohm. The condition indicates between Terminal “COM” and Terminal NO is well connected when relay is activated.