Solenoid time constant

Thread Starter

JardaK

Joined Mar 20, 2015
3
Hello,

I have a small problem.
Solenoid has a resistance of 14.2 ohms and an inductance 0.056H is connected in series with a resistance 2.2Ohm
Thus calculated is the Tau = L / R = 0,056 / (14.2 + 2.2) = 0.0034s
But the measured value is 0.02s
The measurement is done on an oscilloscope for resistance.
Source is a classic laboratory.

If I measure only air-core coil corresponds to the time constant.
How is it possible that tau is based on much more?

Solenoid Type:
Code:
 http://docs-europe.electrocomponents.com/webdocs/001b/0900766b8001b732.pdf [/ code]

Thank you for your response.
 

Alec_t

Joined Sep 17, 2013
14,280
Did you measure with the plunger extended or retracted? Plunger position will probably have a significant effect on inductance.

Edit: I don't think you should count the 14.2 Ohms as being in series with the coil when calculating Tau. So Tau = 0.056/2.2 = 0.025 s
 
Last edited:

Thread Starter

JardaK

Joined Mar 20, 2015
3
Why?
A formula please?
Coil having no core has a smaller inductance. This coil inductance and resistance 0.012H and 14.2Ohm
0.0012 / (14.2 + 2.2) result corresponds approximately
 
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