8. Connection of the Transducers
8. CONNECTION OF THE TRANSDUCERS
Any ALMEMO
®
sensors can be connected to the ALMEMO
®
input sockets M0
to M8 of the measuring instrument (2). For connecting existing sensors it is
only necessary to connect a corresponding ALMEMO
®
connector.
8.1 Transducers
A detailed description of the comprehensive ALMEMO
®
sensor range (see
manual section 3) and the connection of existing sensors (see manual section
4) to the ALMEMO
®
instruments are provided in the ALMEMO
®
manual. All
standard sensors with ALMEMO
®
connector usually have the measuring range
and dimension already programmed and can be immediately connected to any
input socket. A mechanical coding ensures that sensor and output modules
can only be connected to the correct sockets. Furthermore, each ALMEMO
®
connector has two locking levers that snap in when the insertion into the socket
is established and that prevent a disconnection caused by pulling the cable.
Both levers must be pressed on the sides for disconnecting the connector.
8.2 Measuring inputs and Additional Channels
The measuring instrument ALMEMO
®
2890-9 has 9 input sockets (2) that the
measuring channels M0 to M8 are initially allocated to. However, ALMEMO
®
sensors can, if required, provide up to 4 channels so that 36 channels are
available with 5 input sockets. The additional channels can be especially used
with humidity sensors with 4 measuring variables (temperature/humidity/dew
point/mixture ratio) or used for function channels. If required, the sensor can
also be programmed with several ranges or scaling or, depending on the pin
assignment, 2 or 3 sensors can be combined in one connector (e.g. rH/Ntc,
mV/V, mA/V etc.). The additional measuring channels of a connector are in-
creased in steps of 10 (e.g. the first sensor has the channels M0, M10, M20,
M30, the second sensor has the channels M1, M11, M21, M31 etc.).
Device-internal channels:
An innovation on this device is its four extra additional channels. The first of
these M5 is programmed by default as differential channel M1 – M0. This only
happens, however, if there are two sensors with the same units and same dec-
imal point position connected at measuring points M0 and M1. However, all
four channels can be programmed with any other function channels (e.g. U-
Bat, CJ, average, volume flow, etc.); (s. 11.3.10, man. 6.3.4). Mb1 = M1 and
Mb2 = M0 are always used as reference channels by default.
Advantage
of the device-internal channels: If several sensors are being used
for the same application, they do not have to be reprogrammed and can be
freely exchanged without losing their function channels. If, however, the whole
application operates with just one sensor, then programming in the sensor it-
self makes more sense.
On the measuring instrument this gives the following channel assignment:
18 ALMEMO
®
2890-9