Connecting The Transducers; Transducers; Measuring Inputs And Additional Channels - Ahlborn ALMEMO 2490-1A Operating Instructions Manual

CONNECTING THE TRANSDUCERS

8.
Virtually any ALMEMO ® sensor can be connected to ALMEMO ® input socket
M0 (and / or M1 on version 2490-2) on the measuring instrument (1). To connect
your own existing sensors you simply need the appropriate ALMEMO ® con-
nector.

8.1 Transducers

The ALMEMO ® Manual includes detailed descriptions of the comprehensive
ALMEMO ® range of sensors (see Manual Ch 3) and instructions for connecting
your own existing sensors to ALMEMO ® instruments (see Manual Ch 4). All
standard sensors with an ALMEMO ® connector usually have the measuring
range and units already programmed and can thus be connected to any input
socket without further adjustment. A mechanical coding system ensures that
sensors and output modules can only be connected to the correct sockets. All
ALMEMO ® connectors incorporate two snap-lock levers; these snap into posi-
tion as soon as the connector is inserted into the socket, thus preventing unin-
tended disconnection if the cable is accidentally pulled. To withdraw the con-
nector, both these levers must be pressed in at the sides.

8.2 Measuring inputs and additional channels

The ALMEMO 2490-1A has 1 input socket, version 2490-2A has 2 input sock-
®
ets (1); to these initially measuring channels M0 (and M1) are assigned. AL-
MEMO ® sensors can, however, if necessary, provide up to 4 channels. The ad-
ditional channels can be used in particular for humidity sensors with 4 measur-
ing variables (temperature / humidity / dew point / mixture ratio) or for function
channels. Each sensor can if necessary be programmed with several measuring
ranges or scaling settings; and 2 or 3 sensors, if pin assignment so permits, can
be combined in a single connector (e.g. rH / NTC, mV / V, mA / V, etc.). The
additional measuring channel numbers per connector go up in steps of 10 (e.g.
the first sensor has channels M0, M10, M20, M30, the second sensor has chan-
nels M1, M11, M21, M31 etc.).
Device-internal channels (2490-2A only)
A further innovation on this device is its four additional device-internal channels.
The first of these M2 is programmed by default as differential channel M1 – M0.
This only applies, however, if there are two sensors with the same units and
same decimal point position connected at measuring points M0 and M1. How-
ever, all 4 channels can be programmed with any other function channels (e.g.
U-Bat, cold junction compensation, averages, etc.); (see Manual, Section 6.3.4).
The reference channels are by default Mb1 = M1 and Mb2 = M0.
The advantage of device-internal channels is that when using several sensors
for the same application these sensors do not have to be reprogrammed and
can be exchanged without losing the function channels. However, if the whole
application operates with just one sensor, then programming the function chan-
nels on the sensor itself makes more sense.
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