4. CONNECTING THE SENSORS
Any ALMEMO
®
sensors can be connected to ALMEMO
®
input sockets M0 and
M1 (2). To connect your own existing sensors you simply need the appropriate
ALMEMO
®
connector.
4.1 Sensors
The ALMEMO
®
Manual includes detailed descriptions of the comprehensive
ALMEMO
®
sensor range (see Manual, Section 3) and of how to connect your
own existing sensors to ALMEMO
®
instruments (see Manual, Section 4). All
standard sensors with an ALMEMO
®
connector usually have the measuring
range and units already programmed and can thus be immediately connected
to any input socket.
A mechanical code system ensures that sensors and output modules can only
be connected to the correct sockets. Each ALMEMO
®
connector also incorpo-
rates two locking levers; these snap into position as soon as the connector is
inserted into the socket, thus preventing disconnection if the cable is pulled.
To withdraw the connector, both these levers must be pressed in at the sides.
4.2 Measuring inputs and additional channels
Measuring instrument ALMEMO
®
2390-3 has two input sockets M0 and M1 (2)
to which, initially, measuring channels M0 and M1 are allocated. ALMEMO
®
sensors can, however, if necessary, provide four channels. Additional chan-
nels are available primarily for humidity sensors (temperature / humidity / dew
point / mixture ratio) or flow probes and chemical probes incorporating a tem-
perature sensor. A single sensor can be programmed, if necessary, with se-
veral ranges or scaling processes; similarly, if pin assignment permits, two
sensors can be combined on one connector (e.g. rH/Ntc, mV/V, mA/V, etc.).
Measuring point numbering:
Each additional measuring channel in a connector lies one level higher. In this
new series the levels are now numbered in default decimal form, i.e. the front
digit indicates the level. In this way the measuring point number (and thus also
the programmed reference channels) for all devices with 1, 2, 5, or 10 inputs
always remains the same. This means, however, that, with effect from measu-
ring channel number 20, the measured value resolution in the display is limited.
If this proves to be a serious problem, it is possible to revert to continuous se-
quencing - by holding down th eM
▲
key when the device is switched on.
Device-internal channels:
A further innovation on this device is its four extra additional channels. The
first of these is programmed by default as differential measuring channel M1 -
M0. This only appears, however, if there are two sensors with the same units
and same decimal point position connected at measuring points M0 and M1.
12
ALMEMO
2390-3
Connecting the sensors