How to Convert a Milliwatt Meter to Volts
A watt meter is a device used to measure the electrical power of a circuit. A milliwatt meter does this on a smaller scale because 1 watt (W) is equal to 1,000 milliwatts (mW). With a milliwatt meter, it's possible to measure low levels of power, such as radio frequency (RF). Each device is calibrated for a specific circuit resistance, measured in ohms (Ω).
If you know the power and resistance of an electrical system, use Ohm's law to calculate the voltage:
E = sqrt(P * R)
Where:
E = voltage (volts)
sqrt = take the square root
* = multiply
P = power (watts)
R = resistance (ohms)
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Things You'll Need
- Milliwatt meter (either digital or analog)
- Paper
- Pen or pencil
- Calculator
Instructions
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1
Connect the milliwatt meter to your circuit and write down the meter's reading. This will give you a measurement of the electrical power in milliwatts (mW).
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2
Convert your power measurement from milliwatts (mW) to watts (W) by taking the number you recorded in Step 1 and dividing it by 1,000. Write down this value.
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3
Determine what resistance (in ohms, Ω) your milliwatt meter is calibrated to. This should be noted either on the device or in the device manual. An example of a typical resistance level is 50 ohms.
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4
Using your calculator, take the power value (in watts, from Step 2) and multiply it by the resistance value (in ohms, from Step 3). Write down this value.
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5
Using your calculator, take the square root of the value from Step 4. This will give you the voltage in volts.
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1
Tips & Warnings
Alternatively, once you know the power measurement and the resistance values, you can use free online conversion tools to convert these values into the voltage (see Resources). This will save you from doing any calculations.
Remember that the milliwatt meter gives a measurement of power in milliwatts, not watts. The Ohm's law equation works only when the power measurement is in watts. So make sure you don't skip the conversion in Step 2.
References
Resources
- Photo Credit electricity image by jeancliclac from Fotolia.com
