Configuration and operation
akYtec GmbH · Vahrenwalder Str. 269 A · 30179 Hannover · Germany · Tel.: +49 (0) 511 16 59 672-0 · www.akytec.de
17
AIn INT
=
AIn REAL
* 10
DP
DP –
Decimal point offset
specified in the range 0…7.
NOTE
Setting the “Decimal point offset” to 6 or 7 can cause that the “AIn INT” value goes be-
yond the range -32768…32767 (or 0…65535 for unsigned presentation) and cannot be
saved in INT16 format. This should be taken into account when setting the “Decimal point
offset” value.
AIn timestamp
is a cyclic time with the 0.01 second step, stored in two bytes. The time counting starts with
the first measuring and is reset to zero every 65536 steps, i.e. 655.36 seconds. It marks the time of the
measurement in the channel. Using the timestamp, you do not have to take the Ethernet transmission delay
into account (e.g. when calculating the derivation time in the PID control).
The measured values are stored in their respective memory registers (Tab. D.1) and can be read with Mod-
bus functions 3 (0x03) or 4 (0x04).
4.8.6 Sensor diagnostic
The module monitors the operation of the transmitters connected to its inputs. If a malfunction is detected,
the module transmits an error message over Ethernet. Common error cases:
−
All transmitter types – the measured values are beyond the permissible range
−
RTD or TC sensor break
−
RTD short circuit
−
Cold junction temperature is beyond the range -
40...+90 °С
Some transmitter errors cannot be detected:
−
Current and voltage sensor breaks. The measuring channel shows a zero value or the error "Meas-
ured value too low".
−
Due to the implemented diagnostic of a thermocouple short circuit, resistance signals below 25
Ω
are considered invalid. Therefore, the resistance sensor 0...2 k
Ω
cannot measure signals in the
range 0…25
Ω
(0…1.26% of the measuring range).
In case of an input error, the error code is written to the most significant byte of the corresponding
AIn REAL
register instead of the measured value and to the
AIn status
register.
Table 4.7. Input diagnostic errors
Error
code
Description
Input
indicator
0xF0
Incorrect value
orange
0xF6
Data not ready. Wait for the results of the first measurement after powering on.
orange
0xF7
Input disabled (Off)
off
0xF8
Cold junction temperature too high
orange
0xF9
Cold junction temperature too low
orange
0xFA
Measured value too high
orange
0xFB
Measured value too low
orange
0xFC
Sensor short circuit
red
0xFD
Sensor break
red
0xFE
No connection with ADC
red
0xFF
Incorrect calibration coefficient
orange
4.8.7 Reference junction compensation
The input circuit provides an optional correction of the measured values for thermocouples using the refer-
ence (cold) junction temperature compensation (CJC). The cold junction temperature is measured by three
