All HMP155 models (HMP155A, HMP115E, and HMP155D) have an RS-485 connection available for service purpose.
To have a temporary RS-485 connection in the passive output version (HMP155D), hold down the ADJ button when switching on the probe, see Figure 1. When HMP155 starts, pins 2 and 6 have the RS-485 signal. After the next startup, the default signals return to the pins.
The active output version with 2 voltage channels (HMP155A) includes also a solid RS-485 connection with dedicated signal pins that can be used as a temporary digital service port.
| Do not use both digital and analog outputs in parallel continuously. It may affect the temperature measurement accuracy due to increased power consumption and probe self-heating. |