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Author Topic: Keithley Sourcemeter DIGOUT Protection ?  (Read 685 times)

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Offline JohnPiTopic starter

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Keithley Sourcemeter DIGOUT Protection ?
« on: September 10, 2022, 05:31:45 am »
The Keithley Sourcemeters (e.g. 2400) have digital output pins -- DIGOUT. This is shown in the manual as suitable for driving a relay, but no protection against coil inductive spikes is shown. Does it not have protection ? Do I have to add my own diode ?

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Offline gamalot

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Re: Keithley Sourcemeter DIGOUT Protection ?
« Reply #1 on: September 10, 2022, 06:32:43 am »
The diode in the picture (in series with a resistor) is probably what you're expecting, maybe they've drawn the diode's polarity reversed.  :-//

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Sorry I looked again, that diode and resistor should be for pull-up the output.
« Last Edit: September 10, 2022, 07:55:59 am by gamalot »
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Offline Kleinstein

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Re: Keithley Sourcemeter DIGOUT Protection ?
« Reply #2 on: September 10, 2022, 08:53:26 am »
The diode to protect from the inductive kickback of the relay should be at the relay. If in doubt add a 2nd diode - it does not hurt.
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Offline JohnPiTopic starter

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Re: Keithley Sourcemeter DIGOUT Protection ?
« Reply #3 on: September 10, 2022, 04:34:32 pm »
No, that diode is probably to prevent an external > 5 V signal from damaging the internal 5 V supply by pulling it up.

I'll have to add external diodes to clamp the inductance.
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