Help needed: Using a voltmeter

marcdsgn · 07-22-2008, 03:56 PM

I've got hold of a voltmeter to test my old flashes' voltages (to make sure they're compatible with the K10D). Problem is: I have no idea how to use a voltmeter. So this is where you clever lot come in.

Please refer to the image below, and tell me what the heck I'm supposed to do with this thing!!

Thanks in advance. Will check back later in the day to read the thousands of constructive responses.

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MrApollinax · 07-22-2008, 04:01 PM

I'd need a picture of the bottom of the flash but you need to meaure the negative and positive contacts of the flash. I think the negative contact (ground) would be the edges of the hot shoe connection and the postive connection would be on the center of the connector. Post a picture of your flash connection and we should be able to help you.

**kmccanta** · 07-22-2008, 04:07 PM

but it depends on the flash.

*If the flash trigger voltage is present all the time that the flash is ready to fire...*

*this is my guess. If the high flash voltage is only present briefly when the flash fires... then I guess you would need a triggerable 'scope.

Anyway, under assumption #1... put the black cable into the COM hole. put the red cable into the V DC hole.

turn the dial to the V DC 2000m position. this sets the resolution of the display to 2000mV DC. (or 2V) I agree with the guess that the red probe goes on the center flash contact, the black on the outside contact.

If the reading flashes or says E or some other indication that might mean it is out of range, you should try moving the dial to 20 or 200m .

please post photos of the whole thing in action if you can.

sewebster · 07-22-2008, 04:08 PM

Doesn't a flash change voltages very quickly? ie. jump to a high voltage when it discharges, but that only lasts for a fraction of a second? If so, the voltmeter won't be a good idea to use. It won't react fast enough and you won't know what the true peak voltage is. Voltmeters are really only good for measuring steady-state or slowly changing values.

I would try an oscilloscope.

I don't know much about flashes, but a fair amount about voltmeters and oscilloscopes...

**Tyama** · 07-22-2008, 04:58 PM

To use your voltmeter to test a DC voltage in the range of voltage your likely to see ( 3-180 vdc ) set the mode dial on your meter to the 200 position on the V -- portion of the meter . Two clicks counterclockwise from where the dial is in the picture.

Turn the flash on and touch the red lead of the meter to the center contact of the flash and the black lead to one of the other contacts. You should see a voltage indication when you do this. If I remember right it should be under 15 volts to be used on a K10D.

The flash will fire when the center contact is connected ( shorted ) to one of the other contacts which is what the camera does when it fires the flash. The voltage will be present whenever the flash is turned on.

I tested the voltage on an old Sunpak 422D and compared it to my AF 540. The 422D only had three contacts and finding the center one was easy. The AF 540 has five if I remember right, and it's harder to determine the center contact. If you're not sure just touch the red and black leads to the contacts until you get an indication.

timbo13 · 07-22-2008, 05:17 PM

Tyama has it right. I have an old Vivitar flash and got 180 V, this is the way I did it. The voltage is present when the flash is fully charged.

jeffkrol · 07-22-2008, 07:32 PM

Photo Strobe Trigger Voltages
How to measure (yes they could bemisleading due to transient voltage spikes BUT if I remember this correctly high impedence digital meters
work fine, older analog meters are more inclined to miss):
Secrets of Powershot Flash Photography
And image of hot shoe contacts thanks to Mr. Dimitrov
Flash Systems Evolution, Features and Operation

marcdsgn · 07-22-2008, 08:12 PM

Thanks for the info so far, folks. Much appreciated.

Jeffkrol, your links are great. I've bookmarked those for future reference. The mount diagram matches one of my flashes (Vivitar 2600D) which I originally bought for my Pentax MZM. The other flashes are the simple single-contact type. Quite old.

I'll have a go tonight.

07-22-2008, 04:07 PM	#3
kmccanta Site Supporter Join Date: Nov 2006 Location: Portland, Oregon Photos: Gallery Posts: 218	I can guess what you should do... but it depends on the flash. If the flash trigger voltage is present all the time that the flash is ready to fire... *this is my guess. If the high flash voltage is only present briefly when the flash fires... then I guess you would need a triggerable 'scope. Anyway, under assumption #1... put the black cable into the COM hole. put the red cable into the V DC hole. turn the dial to the V DC 2000m position. this sets the resolution of the display to 2000mV DC. (or 2V) I agree with the guess that the red probe goes on the center flash contact, the black on the outside contact. If the reading flashes or says E or some other indication that might mean it is out of range, you should try moving the dial to 20 or 200m . please post photos of the whole thing in action if you can.

07-22-2008, 04:58 PM	#5
Tyama Site Supporter Join Date: Mar 2007 Location: Honolulu, Hawaii Photos: Gallery Posts: 92	To use your voltmeter to test a DC voltage in the range of voltage your likely to see ( 3-180 vdc ) set the mode dial on your meter to the 200 position on the V -- portion of the meter . Two clicks counterclockwise from where the dial is in the picture. Turn the flash on and touch the red lead of the meter to the center contact of the flash and the black lead to one of the other contacts. You should see a voltage indication when you do this. If I remember right it should be under 15 volts to be used on a K10D. The flash will fire when the center contact is connected ( shorted ) to one of the other contacts which is what the camera does when it fires the flash. The voltage will be present whenever the flash is turned on. I tested the voltage on an old Sunpak 422D and compared it to my AF 540. The 422D only had three contacts and finding the center one was easy. The AF 540 has five if I remember right, and it's harder to determine the center contact. If you're not sure just touch the red and black leads to the contacts until you get an indication. Last edited by Tyama; 07-22-2008 at 05:34 PM. Reason: Voltge correction and grammar

07-22-2008, 07:32 PM	#7
jeffkrol Veteran Member Join Date: Sep 2006 Location: Wisconsin USA Photos: Gallery Posts: 8,434	Trigger voltage ect: Photo Strobe Trigger Voltages How to measure (yes they could bemisleading due to transient voltage spikes BUT if I remember this correctly high impedence digital meters work fine, older analog meters are more inclined to miss): Secrets of Powershot Flash Photography And image of hot shoe contacts thanks to Mr. Dimitrov Flash Systems Evolution, Features and Operation

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07-22-2008, 04:01 PM	#2
MrApollinax Veteran Member Join Date: Apr 2008 Location: Minnesota Photos: Gallery Posts: 1,529	I'd need a picture of the bottom of the flash but you need to meaure the negative and positive contacts of the flash. I think the negative contact (ground) would be the edges of the hot shoe connection and the postive connection would be on the center of the connector. Post a picture of your flash connection and we should be able to help you.

07-22-2008, 04:08 PM	#4
sewebster Veteran Member Join Date: Jun 2008 Location: Vancouver, BC Photos: Gallery Posts: 544	Doesn't a flash change voltages very quickly? ie. jump to a high voltage when it discharges, but that only lasts for a fraction of a second? If so, the voltmeter won't be a good idea to use. It won't react fast enough and you won't know what the true peak voltage is. Voltmeters are really only good for measuring steady-state or slowly changing values. I would try an oscilloscope. I don't know much about flashes, but a fair amount about voltmeters and oscilloscopes...

07-22-2008, 05:17 PM	#6
timbo13 Veteran Member Join Date: Mar 2008 Location: Northboro MA, USA Photos: Gallery Posts: 1,007	Tyama has it right. I have an old Vivitar flash and got 180 V, this is the way I did it. The voltage is present when the flash is fully charged.

07-22-2008, 08:12 PM	#8
marcdsgn Senior Member Join Date: Dec 2007 Location: Queensland Photos: Gallery Posts: 265 Original Poster	Thanks for the info so far, folks. Much appreciated. Jeffkrol, your links are great. I've bookmarked those for future reference. The mount diagram matches one of my flashes (Vivitar 2600D) which I originally bought for my Pentax MZM. The other flashes are the simple single-contact type. Quite old. I'll have a go tonight.