GPM40-U USB CW Power Sensor

GPM40-U is a USB CW power sensor for field testing, production line testing and system integration. Its USB interface connects power measurement to a host computer display.

The maximum input powers are damage limits, not the measurement range. Exceeding either limit may damage or burn out the sensor.

Low-power measurement. Below -40 dBm, connect the sensor to the DUT and preheat for one hour in a temperature-controlled environment. Set Step Detection to Off, configure an appropriate number of averages and perform External Zero Calibration. Then enable the DUT signal output, wait one minute and observe the results. The results include zero-setting and measurement-noise errors.

Maximum input power. Maximum input power is the highest power the sensor can handle. Exceeding the stated limit may damage or burn out the sensor.

Accuracy conditions. The ±0.25 dB accuracy applies from -40 dBm to +20 dBm with DUT SWR <1.20 and an average count of 128. Below -40 dBm, zero-setting and measurement-noise effects on measurement accuracy increase as the measured power decreases.

Calibration and measurement uncertainty. Calibration uncertainty includes inherent linear deviation, temperature effects and expanded uncertainty arising from sensor calibration. User measurement uncertainty includes this calibration uncertainty plus sensor-to-DUT port mismatch, zero-setting uncertainty and measurement noise.

Zero setting. Zero setting is the sensor’s fixed output deviation when no signal is applied. Non-ideal internal circuits, including amplifier offset and thermoelectric potential, or external interference cause this deviation, which significantly affects low-power measurements. Preheat for one hour in a temperature-controlled environment and perform external zero calibration before testing.

Measurement noise. Measurement noise is the effect of internal circuit noise on the measurement and is more pronounced for small signals. Measurement-noise testing requires one hour of preheating in a temperature-controlled environment followed by external zero calibration.

ADC sampling rate. Maximum sampling rate is the highest conversion rate of the ADC and is a design specification of the sensor.

Measurement reading rate. Maximum measurement rate is the maximum amount of sensor data that can be read per second. It is correlated with aperture time: measurement rate equals 1/aperture time. The reading rate is governed by aperture time and is distinct from the ADC sampling rate.

Measurement uncertainty also includes sensor-to-DUT mismatch, zero-setting uncertainty and measurement noise.