The robust and compact measuring instrument with a probe socket for highly accurate Pt100 probes and two sockets for fast-action thermocouple probes. Readings from up to three additional temperature probes can be shown on the instrument's clear display; measurement data transmission is by radio i.e. wireless. A total of six channels can be collected in this way by the instrument. Using the highly accurate, plug-in Pt100 immersion/penetration probe, a system accuracy of 0.05 °C with a resolution of 0.001 °C is reached. The measurement system is therefore ideally suited for use as a working standard. Data measured by testo 735-1 can be transmitted by infrared to the Testo printer for documentation purposes. If cyclical printing is used, it is also possible to print data on the printer once every minute, for example.