This tool converts Volt-per-Meter to dB-Microvolt-per-Meter.
Enter the linear field strength value and units using the drop down menu:
- V/m
- mV/m
- μV/m
- nV/m
the tool will calculate the equivalent value in dBµV/m
Formula
dBµV/m = 20*Log10(V/m) + 120
This converter is useful where linear field strength numbers are provided but have to be converted to logarithmic scale for other calculations.
Background
Electric fields are measured in volts per meter (V/m). A one Volt electrical potential at a distance one meter away will have an electric field of 1 V/m.
In general a deciBel value is used to represent a ratio of two quantities – typically power or amplitude. However when there’s a suffix like in this case dBµV/m, it represents an absolute value.
dBµV/m is used in electromagnetic field computations to specify the intensity a certain distance away from a transmitter.
The FCC puts limits on the field intensity. For example, over the range of frequencies in the table below, the FCC has stipulated that at a distance of 3 meters, the carrier frequency will not exceed 48 dBµV/m.
Additionally at the frequency ranges starting at 30 MHz and split into bands (e.g. 30 MHz – 88 MHz) there is a limit to the maximum field strength for out-of-band emissions.
RF designers have to keep these limits in mind when designing wireless hardware. Exceeding these limits will result in the product not being approved for commercial use.
Where is this calculator used?
Some instruments like the Electromagnetic Field Meter (EMF) shown in the picture below provide measurement results in V/m.
For example the screen reading in the picture is 205 V/m. Use the tool on this page to convert it to the equivalent value in dBµV/m.
Note that instruments like the one above will not be suitable to determine whether a device passes FCC limits. This is because they don’t have the front-end filtering for example, to determine the value over specific frequency limits. Instead it provides an integrated value over a range that has limited out-of-band rejection capability. The above measurement for instance states Wi-Fi and Phone. Accurate, calibrated field strength measurement products cost many tens of thousands of dollars.
Example Calculation
A value of 205 V/m is equivalent to 166.23 dBµV/m.
The table below shows specific values and the conversion using the calculator above
| Value | dBμV/m |
|---|---|
| 1 V/m | 120 |
| 1 mV/m | 60 |
| 1 μV/m | 0 |
| 1 nV/m | -60 |
Related Calculators
V/m to dBm – use this tool to convert field intensity to power in dBm at the input to a receiver. Both antenna gain and frequency of operation are required.
References
[1] Electric Field on Wikipedia