Environmental Compensation Commands - GMP251

GMP251 User Guide

Document code
M211799EN
Revision
G
Language
English (United States)
Product
GMP251
Document type
User guide
To apply an accurate relative humidity compensation, the temperature and pressure compensation configurations must also match your measurement environment. See the rhcmode, tcmode and pcmode commands for instructions on enabling compensation configuration, and env command for instructions on setting a compensation value.
For more information on environmental compensation and the default (neutral) compensation values used for disabled compensations, see Environmental Compensation on page 13.
Table 1. Env Command
Syntax Description
env<cr> Show current compensation values.

Before using this command, you must enable environmental compensation using the following commands:

  • o2cmode [on]
  • pcmode [on]
  • rhcmode [on]
  • tcmode [on | measured]
env [temp | pres | oxy | hum] [value]<cr> Set new permanent compensation values and store them in EEPROM.

EEPROM:

  • Non-volatile memory, values retained during power off.
  • Number of writes is limited to 30000 cycles by memory implementation.
  • Must only be used for writing permanent values, to avoid wearing out the EEPROM.

temp = Compensation temperature. Range -40 ... +100 °C (-40 ... +212 °F).

pres = Compensation pressure. Range 500 ... 1150 hPa.

oxy = Oxygen content of background gas. Range 0 ... 100 %.

hum = Relative humidity of background gas. Range 0 ... 100 %.

env [xtemp | xpres | xoxy | xhum] [value]<cr> Set new compensation values and store them in RAM.
RAM:
  • Volatile memory that loses the values when probe is reset, and where values are loaded from non-volatile (EEPROM) memory at power-on.
  • Must be used for continuously updated values.

xtemp = Compensation temperature stored in RAM. Range -40 ... 100 °C (-40 ... +212 °F).

xpres = Compensation pressure stored in RAM. Range 500 ... 1150 hPa.

xoxy = Oxygen content of background gas stored in RAM. Range 0 ... 100 %.

xhum = Relative humidity of background gas stored in RAM. Range 0 ... 100 %.

Note: If temperature compensation is configured to use an internally measured value (tcmode is set to measured), it will continuously update the value in RAM, overriding any temperature value that is written to RAM with the ENV command.
Example (Show current compensation values; all compensations are enabled. Note that temperature compensation is in "measured" mode, so the value in use is constantly changing):
env
In eeprom:
Temperature (C) : 25.00
Pressure (hPa) : 1013.00
Oxygen (%O2) : 21.00
Humidity (%RH) : 50.00

In use:
Temperature (C) : 36.40
Pressure (hPa) : 1013.00
Oxygen (%O2) : 19.70
Humidity (%RH) : 93.00
Example (set temperature compensation to setpoint mode, and change temperature setpoint value to 37.2 in RAM):
pass 1300
tcmode on
T COMP MODE : ON
env xtemp 37.2
In eeprom:
Temperature (C) : 25.00
Pressure (hPa) : 1013.00
Oxygen (%O2) : 21.00
Humidity (%RH) : 50.000

In use:
Temperature (C) : 37.2
Pressure (hPa) : 1013.00
Oxygen (%O2) : 19.70
Humidity (%RH) : 93.00
Table 2. O2cmode Command
Syntax Description
o2cmode<cr> Check current oxygen compensation mode.

Possible modes:

o2cmode [on | off]<cr> Change oxygen compensation mode (on or off).
Example (check oxygen compensation mode; oxygen compensation is disabled, a neutral value is used):
pass 1300
o2cmode
O2 COMP MODE : OFF
Example (enable oxygen compensation):
pass 1300
o2cmode on
O2 COMP MODE : ON
Table 3. Pcmode Command
Syntax Description
pcmode<cr> Check current pressure compensation mode.

Possible modes:

pcmode [on | off]<cr> Change pressure compensation mode (on or off).
Example (check pressure compensation mode; pressure compensation is enabled using a setpoint value):
pass 1300
pcmode
P COMP MODE : ON
Table 4. Rhcmode Command
Syntax Description
rhcmode<cr> Check current relative humidity compensation mode.

Possible modes:

To apply an accurate relative humidity compensation, make sure that the temperature compensation and pressure compensation configurations also match the measurement environment.
rhcmode [on | off]<cr> Change relative humidity compensation mode (on or off).
Example (check relative humidity compensation mode; relative humidity compensation is disabled, a neutral value is used):
pass 1300
rhcmode
RH COMP MODE : OFF
Example (enable temperature, pressure and relative humidity compensation using setpoint values):
pass 1300
tcmode on
T COMP MODE : ON
pcmode on
P COMP MODE : ON
rhcmode on
RH COMP MODE : ON
Table 5. Tcmode Command
Syntax Description
tcmode<cr> Check current temperature compensation mode.

Possible modes:

  • on = Compensation enabled using setpoint value.
  • off = Compensation disabled, default (neutral) value used: see Environmental Compensation on page 13.
  • measured = Compensation enabled using internal measurement.
tcmode [on | off | measured]<cr> Change temperature compensation mode (on, off or measured).
Example (check temperature compensation mode; temperature compensation is enabled using a setpoint value):
pass 1300
tcmode
T COMP MODE : ON
Example (change temperature compensation to use internal measurement):
pass 1300
tcmode measured
T COMP MODE : MEASURED