The Keysight U1242B 4-digit handheld digital multimeter (DMM) is designed for quick checks and fixes in the installation and maintenance of machinery, facility and electrical systems. Key capabilities include the switch counter for the detection of glitches on facility switch and relay systems. The harmonic ratio function helps detect the presence of harmonics in AC supplies that can lead to overheating of motors, generators and transformers. The U1242B also enables dual and differential temperature measurements for heating, ventilation and air-conditioning (HVAC) systems. Monitoring differential temperature in real-time is especially useful in making sure that HVAC components in the system are cooling or heating the way they should with respect to time. With the U1242B, you can perform inspections quickly and conveniently with the same troubleshooting tool that you carry on your daily rounds.