Calibration-related Modbus registers and functions - HMP1 - HMP110 - HMP3 - HMP4 - HMP5 - HMP7 - HMP8 - HMP9 - HMPX - MMP8

Note that register availability varies depending on the probe model (for example, RH registers are not applicable for T-only probes).

Modbus calibration registers (writable)
Register number	Address	Register description	Data format	Unit/Valid range
8193	0x2000	Calibration mode passcode	16-bit integer	1300 = calibration mode enabled Any other value = calibration mode disabled
8194	0x2001	Calibration year	16-bit integer	These 3 registers must be written in a single transaction. It is not possible to change only year/month/day alone; such attempt will be ignored.
8195	0x2002	Calibration month	16-bit integer
8196	0x2003	Calibration day	16-bit integer
8197	0x2004	Calibration text	text	Text string in UTF-8 encoding, maximum 24 bytes (23 bytes on HMP110). When writing a new calibration text, all Modbus registers in this range must be written, even if the text is shorter. The written text must be filled with NUL bytes so that it exactly 12 registers (24 bytes) long. Any write attempts not writing all these registers in one transaction will be ignored.
	0x2005
	0x2006
	0x2007
	0x2008
	0x2009
	0x2010
	0x2011
	0x2012
	0x2013
	0x2014
	0x2015
User RH adjustment
8449	0x2100	Reference RH value, point 1	32-bit float	%RH
8449	0x2101	Reference RH value, point 1	32-bit float	%RH
8451	0x2102	Measured RH value, point 1	32-bit float	%RH
8451	0x2103	Measured RH value, point 1	32-bit float	%RH
8453	0x2104	Measured T value, point 1	32-bit float	°C
8453	0x2105	Measured T value, point 1	32-bit float	°C
8455	0x2106	Reference RH value, point 2	32-bit float	%RH
8455	0x2107	Reference RH value, point 2	32-bit float	%RH
8457	0x2108	Measured RH value, point 2	32-bit float	%RH
8457	0x2109	Measured RH value, point 2	32-bit float	%RH
8459	0x210A	Measured T value, point 2	32-bit float	°C
8459	0x210B	Measured T value, point 2	32-bit float	°C
8461	0x210C	Reference RH value, point 3	32-bit float	%RH
8461	0x210D	Reference RH value, point 3	32-bit float	%RH
8463	0x210E	Measured RH value, point 3	32-bit float	%RH
8463	0x210F	Measured RH value, point 3	32-bit float	%RH
8465	0x2110	Measured T value, point 3	32-bit float	°C
8465	0x2111	Measured T value, point 3	32-bit float	°C
8467	0x2112	Reference RH value, point 4	32-bit float	%RH
8467	0x2113	Reference RH value, point 4	32-bit float	%RH
8469	0x2114	Measured RH value, point 4	32-bit float	%RH
8469	0x2115	Measured RH value, point 4	32-bit float	%RH
8471	0x2116	Measured T value, point 4	32-bit float	°C
8471	0x2117	Measured T value, point 4	32-bit float	°C
8473	0x2118	Reference RH value, point 5	32-bit float	%RH
8473	0x2119	Reference RH value, point 5	32-bit float	%RH
8475	0x211A	Measured RH value, point 5	32-bit float	%RH
8475	0x211B	Measured RH value, point 5	32-bit float	%RH
8477	0x211C	Measured T value, point 5	32-bit float	°C
8477	0x211D	Measured T value, point 5	32-bit float	°C
User T adjustment
8705	0x2200	Reference T value, point 1	32-bit float	°C
8705	0x2201	Reference T value, point 1	32-bit float	°C
8707	0x2202	Measured T value, point 1	32-bit float	°C
8707	0x2203	Measured T value, point 1	32-bit float	°C
8709	0x2204	Reference T value, point 2	32-bit float	°C
8709	0x2205	Reference T value, point 2	32-bit float	°C
8711	0x2206	Measured T value, point 2	32-bit float	°C
8711	0x2207	Measured T value, point 2	32-bit float	°C

Modbus function registers (writable)
Register number	Address	Register description	Data format	Unit/Valid range
Functions
1285	0x0504	Start sensor purge	16-bit integer	When writing to register: 1 = Start sensor purge When sensor purge is in progress, the value of the register will count up from 0 to 100. When the value returns to 0, the sensor purge is complete.
8479	0x211E	Activate RH adjustment	16-bit integer	When writing to register: 1 = Activate RH adjustment
8480	0x211F	Restore factory RH adjustment	16-bit integer	When writing to register: 1 = Restore factory RH adjustment
8713	0x2208	Activate T adjustment	16-bit integer	When writing to register: 1 = Activate T adjustment
8714	0x2209	Restore factory T adjustment	16-bit integer	When writing to register: 1 = Restore factory T adjustment

Adjustment function return codes
Value	Meaning
0	Adjustment successful
-1	Adjustment failed due to missing or incorrect calibration values
-2	Adjustment failed, calibration locked
-4	Adjustment failed, calibration points too close to each other
-5	Adjustment failed, cumulative correction too large ¹
-6	HMP110 only: Adjustment failed, multipoint calibration points not compatible with each other

¹ This code may indicate that the sensor is at the end of its life cycle and must be replaced. If adjustment attempts repeatedly produce this return code, consider replacing the sensor. Before replacing the sensor, ensure that no mistakes have been made in the adjustment (for example, rule out possible issues caused by insufficient stabilization time or quality of adjustment reference). See probe documentation for adjustment requirements.

Calibration-related Modbus registers and functions - HMP1 - HMP110 - HMP3 - HMP4 - HMP5 - HMP7 - HMP8 - HMP9 - HMPX - MMP8 - TMP1

Calibrating and adjusting HMP Series and HMP110 probes using Modbus Technical Note