Sensors
3 subcategories
RF, microwave, and optical power sensors are critical instruments for quantifying the signal power of transmitters, transmission lines, and optical components. Used by design engineers and calibration technicians, these sensors convert electromagnetic or optical power into readable electrical signals. When selecting a power sensor, engineers must evaluate the underlying detection technology—such as diodes, thermocouples, thermistors, or optical semiconductor detectors—against the signal's frequency, power level, and modulation. Choosing the correct sensor topology ensures minimal measurement uncertainty, appropriate dynamic range, and accurate tracking of either average power or fast pulse envelopes.
- Frequency Range
- 9 kHz to 110 GHz
- Optical Wavelengths
- 800 nm to 1700 nm
- Power Range
- -70 dBm to +44 dBm
- Key Sensing Elements
- Diode, Thermocouple, Thermistor, InGaAs
Subcategories
Sensor Technologies and Sensing Elements
Power sensors rely on distinct sensing technologies to match specific test scenarios. Thermocouple-based sensors, such as the Keysight Technologies (Agilent HP) 8481A and Keysight Technologies (Agilent HP) 8485A, utilize thermal heating to measure true average power. Thermocouples handle complex modulated signals without bandwidth limitations, offering moderate dynamic ranges like -30 dBm to +20 dBm. High-power thermocouple variants like the Keysight Technologies (Agilent HP) 8481B integrate 30 dB attenuators to measure levels up to +44 dBm (25 W). For high-precision standards lab applications, coaxial thermistor mounts like the Keysight Technologies (Agilent HP) 478A provide temperature-compensated reference measurements.
Diode sensors, such as the Keysight Technologies (Agilent HP) E4413A and Keysight Technologies (Agilent HP) E4412A, leverage the square-law characteristics of semiconductor diodes. They offer significantly higher sensitivity, enabling dynamic ranges up to 90 dB (from -70 dBm to +20 dBm), but require careful compensation when measuring non-CW or modulated waveforms. In the optical domain, sensors like the Keysight Technologies (Agilent HP) 81536A and Keysight Technologies (Agilent HP) 81635A use Indium Gallium Arsenide (InGaAs) photodetectors to cover wavelengths from 800 nm to 1700 nm, managing power ranges down to -70 or -80 dBm.
Dynamic Range, Bandwidth, and Modulated Signals
Selecting a sensor requires matching its video bandwidth and rise time to the target signal. Average power sensors, such as the Keysight Technologies (Agilent HP) E9300A or Keysight Technologies (Agilent HP) U2002A, measure the integrated energy of the signal over time but cannot capture rapid envelope variations.
For pulsed RF environments, peak and wideband power sensors are essential. The Keysight Technologies (Agilent HP) N1921A and Keysight Technologies (Agilent HP) N1922A offer a 30 MHz video bandwidth and rise/fall times of ≤ 13 ns. This fast response allows the sensors to capture peak, average, and peak-to-average ratios on complex broadband modulated waveforms. Intermediate sensors like the Keysight Technologies (Agilent HP) E9322A and Keysight Technologies (Agilent HP) E9325A provide selectable video bandwidths up to 1.5 MHz or 300 kHz, optimizing rise times for specific telecommunication standards.
Interface and Mainframe Compatibility
Engineers must choose between legacy host-dependent sensors and modern standalone USB architectures. Standard legacy sensors require a dedicated power meter or mainframe to supply power and process data. For example, sensors like the Keysight Technologies (Agilent HP) 8484A, Keysight Technologies (Agilent HP) 8481D, and Keysight Technologies (Agilent HP) 8482B connect to host meters using multi-pin sensor cables. Similarly, optical modules like the Keysight Technologies (Agilent HP) 81630B fit directly into Lightwave mainframe slots to share displays and control interfaces.
Conversely, USB power sensors like the Keysight Technologies (Agilent HP) U2000A, Keysight Technologies (Agilent HP) U2001A, and Keysight Technologies (Agilent HP) U2004A operate as independent, standalone instruments. They plug directly into a PC via USB 2.0, draw bus power, and perform internal analog-to-digital conversion, eliminating the footprint and cost of an external power meter mainframe.
Frequently asked questions
- What is the main difference between thermocouple and diode power sensors?
- Thermocouple sensors, such as the Keysight Technologies (Agilent HP) 8481A, measure average power directly through heat generation, making them highly accurate for all modulation formats but limited to a narrower dynamic range (typically -30 dBm to +20 dBm). Diode sensors, like the Keysight Technologies (Agilent HP) E4412A, use semiconductor junctions to achieve high sensitivity and wide dynamic ranges (typically -70 dBm to +20 dBm) but require attenuation or advanced dual-path architectures to accurately measure complex modulated signals.
- When is a wideband peak power sensor required instead of an average power sensor?
- A wideband peak power sensor, such as the Keysight Technologies (Agilent HP) N1921A, is required when you need to characterize fast signal envelopes, pulse widths, rise/fall times, or peak-to-average power ratios. These sensors provide high video bandwidth (up to 30 MHz) and sub-microsecond rise times, whereas average power sensors can only resolve the integrated average power of a transmission.