11. Measuring with the measuring menus
The atmospheric pressure is set to 1013 mbar with each reset. It can be set to
the current value at any time using the usual data input process; (see 10.5). If
atmospheric pressure is being used for compensation in a measuring menu the
symbol ´CP´ is displayed; if atmospheric pressure is itself being measured the
measured value is displayed and a dot flashes after ´
CP
´.
Please note that as soon as a reference sensor is disconnected
normal pressure, 1013 mbar, is used.
11.2.7 Cold junction compensation
Cold junction compensation (CJ) for thermocouples is normally performed
completely automatically. On this device, with 9 sockets, to ensure the highest
possible degree of accuracy - even in difficult thermal conditions (e.g. thermal
irradiation) - the socket temperatures are acquired by means of two precision
NTC sensors in measuring sockets M0 and M8 and then calculated by linear
interpolation. The mean cold junction temperature is displayed as an operating
parameter in the device configuration (see 12.5.8). This can if necessary be in-
corporated in measured data acquisition as device temperature with function
channel ´CJ´ (see 12.3.10).
Instead of this form of cold junction temperature measurement it is also possi-
ble to use an external measuring sensor (Pt100 or NTC) in an isothermal block
(see Manual 6.7.3); this must be positioned upstream from the thermocouples
and ´*J´ must have been programmed in the first two positions in the designa-
tion (see 12.3.2). In this mode the device is switched over automatically to
´continuous measuring point scan´.
For especially exacting requirements (e.g. for thermocouples for which there is
no connector with thermo-contacts or for large temperature differences caused
by thermal irradiation) special connectors are available, each with its own inte-
grated temperature sensor (ZA-9400-FSx) for cold junction compensation.
These can be used for all thermocouple types; however, they require two mea-
suring channels. Having ”#J” programmed in the first two positions in the des-
ignation for the thermocouple ensures that the temperature sensor integrated
in the connector is indeed used for cold junction compensation.
36 ALMEMO
®
5690-2M
