IMC CANSAS - Heartbeats

To Next Page

To Previous Page

124 Operation

3.5.9 Heartbeats

All imc CANSAS-modules (excepting imc µ-CANSAS modules and imc µ-CANSAS-HUB4) can be made to

transmit a so-called heartbeat message via the CAN-Bus. This message is basically a sign of life from the

module. Just like an animal's pulse proceeds at a regular pace, this type of message works the same way.

A master which monitors the entire CAN-Bus can thus determine on the basis of the regularly

transmitted message whether a module is still alive (meaning: at least working well enough to send this

message).

It is thus seen that this heartbeat message is mainly useful for output modules which don't send

messages on their own but rather wait to first receive other messages from the CAN-Bus. Such modules

include the DAC8 (analog outputs), the DO16 (digital outputs) or the DO16R (relay) or the PWM8 module

(pulse-width modulated output). Without the heartbeat message, the bus master would hardly or only

indirectly be able to recognize whether the modules are working at all.

Such a master exists in many situations, e.g., a test rig PC, which controls the overall test station, a

guidance system or an automation system.

But the emission of heartbeats is also useful for modules which actually send their measurement data at

regular intervals as CAN-messages via the CAN-Bus. The heartbeat message contains important

information: The module's serial number and a 'Magic number' for its configuration. and additionally, in

the case of sensor-detecting modules such as UN8, a bit which reflects whether the correct sensors are

connected. On the basis of this number, the guidance system can determine the following:

Is the correct imc CANSAS unit installed? Or could someone have removed and replaced it with a

different one, which either is or isn't configured the same way? An experiment setup's record may

include info on the measurement equipment used and its calibration. If the device was exchanged,

this info would be missing. This situation can at least be detected.

Is the module configured as it is supposed to be? Naturally, the data-recording measurement

system must be able to rely on the imc CANSAS module being configured as it should be. Otherwise,

acquired data may be interpreted incorrectly. If the imc CANSAS-module was reconfigured, it's at

least possible to detect.

In the case of sensor-recognizing modules it is even possible to notice whether the correct sensors

are connected.

All this information isn't directly relevant to conducting a single, classical lab experiment. But at test

stations where different personnel set up and conduct a variety of measurements, it can be crucial.

The heartbeat-message is set in the user interface by selecting the entry Special functions in the tree at

left, and going to the Heartbeat index card on the right-hand side.

Other manuals for IMC CANSAS