vivitar trigger voltage

[macronikon]

<p>have been reading the forums about this and i went down and got a multimeter and checkec the voltage and it was 9.8. mt 283 is late 1990 or early 2000 and was made in China. hope this helps someone</p>

<p>Macronilon</p>

[tom_harvey3]

<p>Craig, someone has already compiled a large list of flash units and their trigger voltages:<br>

http://www.botzilla.com/photo/strobeVolts.html</p>

[sammy_d1]

<p>You have to be careful, even with a reading from a meter. I have found that most meters cannot measure the initial spike the flash gives, before it settles down to a stable voltage. Over time, the spike may cause a lot of problems. </p>

[steve m smith]

<p>Which initial spike is this?</p>

<p>The trigger circuit is a small capacitor which is charged via a very high value resistor from the main high voltage circuit. So when the flash is switched on, the voltage on the main capacitor starts to rise as it charges. This is closely followed by the voltage on the trigger capacitor. When the flash is fired, this capacitor is discharged into the trigger transformer which drops its voltage down to practically zero.</p>

<p>Once the flash tube is triggered, the main capacitor is quickly discharged through the tube converting its stored energy into light and reducing the main capacitor's voltage back down to zero and it then starts to charge up again ready for the next flash.</p>

<p>So ther is no initial spike of voltage just a slowly rising and quickly dropping voltage which would resemble a sawtooth shape if the flash was repeatedly fired at a high enough rate.</p>

[sammy_d1]

<p>I did some test with a Fluke meter, and another much less expensive meter. The Fluke showed higher voltages, and sometimes showed a very brief spike that I cannot explain. I asked other engineers about it, and they told me that even brief spikes can cause damage over time. Maybe I had an odd flash I was testing, and maybe something is going on that I don't understand. I am not an engineer, but I was nervous enough about it that I quit using it on board. If this information is wrong, I would be quite happy to know about it. I have a number of old flashes that I would like to use. YMMV. </p>

[kelly_flanigan1]

<p>There is a reason the O'scope was invented.</p>

<p>Try "measuring" the voltage of a doorknob with a dumb meter when one walks across a carpet and one gets a shock.</p>

<p>If you want low numbers; just use a handheld meter!</p>

<p>****With a Proper storage O'scope and a high voltage scope probe; one can get *hundreds and thousands of volts* off an older strobe. If one uses a dumb handheld volt meter; one gets low numbers; a false sense of security.</p>

<p>If one wants to be like Beavis and Butthead; use the wrong tools to measure the shock loads on parachute ropes or strobe voltages.</p>

<p>The link mentioned does not even mention what test equipment was used; or its bandwidth and rise time; or its input impedance; or what load if any was used; thus childish and lame; ie dangerous.</p>

<p>Most all handheld meters do not capture a fast transient voltage spike; unless one has a very special one that has a fast front end. ie more like a modern digital storage repair techs meter with a scope like display.</p>

<p>****At best using the wrong tools gives a false sense of security; low numbers . That is why on consumer products like ropes and pulleys they today place low numbers on the ratings; ie the dumbing down of the population.</p>

<p>You might as well be "trying" to measure how bright lightning is at night with a dumb handheld light meter.</p>

<p>It would be better if on that link folks mentioned what meter they used; thus the bogus data earmarked; maybe about all.</p>

<p>What is real sad is most photographers understand that one needs a flash meter to measure strobe's light output' not a Retina IIIc's meter. But somehow the concept of capturing a fast spike with the wrong tool doed not bother the lay here.</p>

[steve m smith]

<p>Kelly is correct. Due to the internal high resistance feeding the trigger capacitor which I mentioned in my previous post, a simple multi-meter will tend to show a lower voltage than is really there due to it's own internal resistance.</p>

<p>e.g. if the flash resistor is 1,000,0000 ohms and the meter's resistance is also 1,000,000 ohms then the displayed voltage is actually half of the actual voltage. In reality the meter's resistance will be higher than this so the error should be lower but there may be cheap meters around which give errors of this magnitude when measuring high resistance circuits.</p>

<p>However, a typical circuit with a 1,000,000 ohm resistor feeding a 0.1uF capacitor is not likely to show any transient spike of voltage even if one is present on the main high voltage circuit (which is also very unlikely).</p>

<p>This very circuit arrangement of a series resistor and a parallel capacitor is common in electronics as a de-coupling or smoothing circuit and it's intention is to reduce spikes and ripple to give a smooth DC level.</p>

[sammy_d1]

<p>Ok, so at the end of all this...? How do we determine whether or not a particular flash is safe? As I wrote earlier, I wasn't going to take the chance, not knowing the intricacies of the electronics involved. Is there a definitive test for a layman? </p>

[steve m smith]

<p>Obviously the safest thing to do is not use it.... if you believe all the stuff about high voltages damaging DSLRs. Personally I think a lot of it is mythology put about to sell more equipment.</p>

<p>A real world test would be to turn on your flash and wait for it to charge to full then use a multi-meter to measure the voltage between the two hotshoe contacts. i.e. the centre pin and the edge contact.<br>

<br />The voltage you read there is the maximum it is ever going to be but due to the multi-meter loading as detailed above, add about 10% to 20% to that reading as a safety margin.<br>

Then read your camera's manual. Most cameras are fine up to 250 volts and even then the SCR used in the camera is probably rated to 400 volts. It is not actually possible to buy an SCR (the component used to trigger the flash) which would be rated as low as 6, 12 or 24 volts (commonly stated maximums). 250 volts is about as low as they are rated.</p>