switching times of relay.

[alphadog]

I would like to measure the switching times (activating and deactivating times) of a latching relay that i posses.
I have a DPDT single coil latching relay, and i shorted the two NOs to each other, the two COMs to each other, and the two NCs to each other, so i actually have SPDT relay.
The NO pin is connected to the AC-mains (230V, 50Hz), and the COM pin is connected to the load (Up to 16Arms load).
To my knowledge:
1.
When the relay is OFF, then no current is flowing through the contacts, and therefore the contacts dont affect switching the relay ON.
Activating time depends only on coil, and doesnt depend on loads.

2.
When the relay is ON, current is flowing through the contacts, and they create an alternate magnetic field which creates an induced current through the coil.
The size of the induced current depends on the load.
Deactivating time depends on coil and on load.


My questions are:
1. are these two claims are correct?

2. How can i measure the deactivating time if it is different for different loads?

Thanks!

 

[Hero999]

Yes it's the coil that matters.

You can measure the speed by connecting the coil in series with the normally closed contacts so it oscillates. Look at the squarewave generated on an oscilloscope, the low part of the cycle is how long it takes for the relay to turn on and the high side of the cycle is how long it takes to turn off.

 

[alphadog]

Thank you for your help hero.
What signals are you represnting on the oscilloscpe?
The first signal is probably the Vcontrol squarewave that de/activates the relay driver.
What is the second signal that you were describing?

Correction:
I had a mistake in the thread, The NO is connected to the AC-mains.

 

[alphadog]

Oh i understand you now!

But it doesnt solve the problem that differents load affect the deactivating time of the relay.

 

[Leftyretro]

"2.
When the relay is ON, current is flowing through the contacts, and they create an alternate magnetic field which creates an induced current through the coil.
The size of the induced current depends on the load.
Deactivating time depends on coil and on load."

This statement is not correct. That is the current flowing or not flowing through the contacts should not have an effect on the switching time of the relay. Here is a typical data sheet for a small relay showing data on it's various specification. You will notice that the timing specs show no relationship nor dependecies on the contact load.

https://www.electro-tech-online.com/custompdfs/2009/02/a.pdf

Lefty

 

[Dean Huster]

Contact bounce will drive you crazy trying to analyze all that on an oscilloscope. To help, make sure that you allow the contacts to be part of a DC circuit vs. an AC circuit.

Dean