An RF power output meter (wattmeter) measures the actual power delivered by an RF signal, typically in watts (W) or dBm.

For example, it can read +30 dBm (1 W), +50 dBm (100 W), or even kilowatt-level signals, depending on the sensor.

Unlike a spectrum analyzer, it measures total power across a frequency range (e.g., 100 MHz to 3 GHz) rather than power at a single frequency, making it ideal for verifying transmitter output and system performance.

A voltmeter measures voltage, while a wattmeter measures power—and that difference matters in RF systems.

A voltmeter reads electrical potential (volts). For example, it might measure 10 V RMS across a load, but that alone doesn’t tell you how much power is being delivered.
A wattmeter measures real power (watts), combining voltage and current. For example, in a 50 Ω RF system, 10 V RMS ≈ 2 W (~+33 dBm), while 70.7 V RMS ≈ 100 W (+50 dBm).

Simple takeaway: A voltmeter tells you how much voltage is present, while a wattmeter tells you how much usable power is actually being delivered to the load.

The two types of wattmeters are analog wattmeters and digital wattmeters - both measure forward and reflected power, but they differ in four key ways.

1. Display: Analog uses a scale and moving pointer while the digital wattmeter uses a numeric display.

2. Signal type: Analog is best for CW signals, while digital accurately measures CW and digitally modulated signals.

3. Elements: Analog wattmeters use narrow band plug-in elements (e.g., 5 W, 50 W, 500 W ranges), while digital wattmeters are element-free.

4. Accuracy: Analog is typically ±5% of reading or ± full scale, while digital wattmeters offer about ±4% accuracy across a wide range (e.g., –20 dBm to +60 dBm).