Ham radio enthusiast and Vernier consultant Lew Malchick was having trouble with one of his radios. The packet system radio is set up to support the Nassau County, NY Amateur Radio Emergency Service (ARES) group, so it was important to keep the radio functioning. Lew’s packet data was being corrupted as the radio switched from receive to transmit, rendering the information unusable. Lew suspected a faulty power supply and connected a voltmeter to watch for irregularities, but nothing showed up. Feeling confident that he knew the cause, he decided to see if he could “see” the problem using a Vernier Differential Voltage Probe and the Logger Pro Software.
Using three 560 kΩ resistors connected in series, Lew wired a resistive voltage divider to monitor the voltage. This was necessary to allow the ±6.0 V Differential Voltage Probe to be used in a circuit with a 13.4 V operational voltage. He measured the voltage drop across one of the resistors and used a calculated column in Logger Pro, multiplying the sensor reading by three, to represent the power supply voltage. Lew set up Logger Pro to collect every tenth of a second and measured the changes in voltage as he used the radio. Sure enough, the power supply voltage dropped to 9.1 V and back in just two tenths of a second. Lew swapped out the power supply and the voltage stayed within the ±0.3 V specification of the radio.