User's Manual

6 Using the product
11
WARNING
Only tighten valve positioner with your hand! Do not use any tools
when tightening as otherwise the thread may be damaged.
6 Using the product
6.1. Preparing for measurement
6.1.1. Connecting the temperature sensor
Sensors must be connected before the measuring
instrument is switched on, so that they are recognised by
the instrument.
Surface temperature sensor
An NTC temperature sensor (accessory) must be connected for
measuring the pipe temperature and for automatic calculation of
superheating and subcooling.
Deactivating the surface compensation factor for insertion and
air temperature sensor
A surface compensation factor has been set in the measuring
instrument to reduce the measuring errors in the main field of
applications. This reduces measuring errors when using surface
temperature sensors.
If the measuring instrument testo 550 is used in combination with
insertion or air temperature sensors (accessories), this factor must
be deactivated:
> Press and hold the keys SET + MODE together and switch on
the measuring instrument [
].
- The instrument shows the message Fact off.
The surface compensation factor becomes active every
time the measuring instrument is switched on.