Xylem Expert 7060_7070_Modbus - Manual (Page 25)

Communication protocol Serie30
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6.3 Error handling and recognition
The electronic unit can read five signals: pressure values from two pressure sensors (P1, P2), temperature values from both of
these pressure sensors (TOB1, TOB2) and temperature value from one additional temperature sensor (T). Additionally, out of
these values an other value can be calculated (CH0). These values are described as channels in this documentation.
To check if the channels are active one may use function F32 (or MODBUS addresses 0x0204-0x0206) (refer to according
chapter).
Measuring range
The signals are being measured with an analogue to digital converter (DAC). The measuring range is limited upwards and
downwards.
For the pressure signals P1 and P2 the limitation is depending on the compensated pressure range, which can be read out with
function 30 (as well as MODBUS function 3 [range 0x03xx] from version 5.20-10.x and later).
Readable range: (pressure range minimum – 10%) up to (pressure range maximum + 10%)
Is the pressure below or above this range, then the bit in the Status-Byte will be set. The measured value itself is no longer valid
when the Status-Bit is set.
Dependencies
P1 and P2 are temperature-compensated and therefore they are depending on temperature. Channel CH0 is always depending
on P1 and / or P2 and on a temperature channel. Is there a fault in one of these dependencies so the depending channel will
follow accordingly.
6.3.1 What is new in version 5.20-10.40 (and later)
Version 5.20-10.40 (available end of 2010) and later will display additionally to the Status-Bit also an error in the value itself.
The format follows the special indications according to floating point arithmetic: NaN, +Inf (ovl), -Inf (uvl). See chapter floating-
point Format IEEE754.
CH0 P1/P2 TOB1/TOB2
NaN Dependency error (P1, P2 = NaN or +/-
Inf)
+/-Inf in compensating T-channel -
+Inf - ADC value out of range (Overflow) ADC value out of range (Overflow)
T > 300 °C
-Inf - ADC value out of range (Underflow) ADC value out of range (Underflow)
T < - 70°C
0.000 Sqrt( < Pcutoff ) - -
The values NaN, +Inf and –Inf are defined in the IEEE754 standard and are described in chapter floating-point format IEEE754.
NaN is also shown, when the requested channel is not active. In this case, the Staus-Bit is not set.
Integer Values (Function 74):
ovl Æ 2147483647
uvlÆ -2147483648
NaN Ж 2147483647