How to Check the Firing Voltage for Your Flash

Some older flashes can use trigger voltages as high as 600 volts.

Many newer digital cameras can use only flashes with a low trigger voltage, also known as a firing voltage. Camera flashes work by applying a trigger voltage to a tube full of gas, causing the main capacitor to discharge suddenly. This makes the gas light up, and allows you to take a well-lit picture. High voltages, such as those found in older flash units, can damage your camera severely. You can check the voltage on your flash using a multimeter.

Things You'll Need

• Flash unit manual
• Digital multimeter

Instructions

1. Look for information about your flash unit. If you still have the manual, check the flash specifications. If you no longer have the manual, email or telephone the manufacturer's customer support department to ask about your particular model.

2. Charge the flash. Put fresh batteries in the flash for which you wish to check the voltage. Charge the flash until the ready lamp lights up.

3. Prepare the meter. Set the digital multimeter's range selector to its most sensitive range.

4. Meter the flash. Hold the black, or negative, probe to your flash's edge contact, and the red, or positive, probe to the center pin. The flash voltage should appear on the multimeter's digital display.

Tips & Warnings

• Check your camera type to determine flash compatibility; different camera makes and models have different voltage tolerances.

• Use online resources to look up your flash voltage if you don't have a manual.

• Analog voltmeters may provide inaccurate readings.

References

• N. David King: Electronic Cameras vs. Trigger Voltage [PDF]
• DPAnswers: Checking Trigger Voltage
• Botzilla: Strobe Trigger Voltages
• C-K's Digital Camera Page: Trigger Voltage