Which device is needed to connect to a gas heating thermocouple for testing under a no load condition?

When testing a gas heating thermocouple under no load conditions, a millivolt meter is the appropriate device to use. A thermocouple generates a small voltage (in millivolts) when exposed to temperature differences, and this generated voltage is used to determine if the thermocouple is functioning correctly. The millivolt meter is specifically designed to measure low voltage output, which makes it ideal for assessing the performance of a thermocouple.

Using this meter, a technician can check the voltage output from the thermocouple in response to the heat source, allowing for an assessment of whether it is operating within acceptable parameters. This is essential for troubleshooting and ensuring the heating system operates safely and effectively.

In contrast, other devices like an ammeter measure current, a manometer is used for measuring gas pressure, and an ohmmeter measures resistance, none of which are suitable for testing the voltage output of a thermocouple. Thus, the millivolt meter is essential for evaluating the thermocouple's performance under no load conditions.