IN-E-HyFlex-V4_10
Rotronic AG
Bassersdorf, Switzerland
Document code
Unit
Instruction Manual
Document Type
HygroFlex transmitter version 4: instruction
manual
Document title
Page
13
of 61
© 2006; Rotronic AG IN-E-HyFlex-V2_10.doc
4.1 Internal service connector (HygroFlex configuration)
All HygroFlex models have an internal RS-232 service connector (
MTA
) located on the main PCB
(see
PCB connections
). Cable AC1623 is required to connect the HygroFlex
MTA
connector to
COM port of a PC.
Use of the MTA service connector is limited to configuring the instrument (unit system, output
range, display, etc.). Both the HygroFlex 2 and HygroFlex 3 can also be configured via one of the
external digital ports.
Instrument configuration requires a PC with the HW4 software installed. Instructions for configuring
the HygroFlex are provided in the software manual.
4.2 Resolution of the analog signals (HygroFlex 3)
The HW4 software allows defining the range of the analog output signals of the HygroFlex 3. When
selecting a range, it is important to consider the fact that the resolution of the analog output signal
depends on the span of the selected range.
The HygroFlex 3 uses two 12-bit D/A converters to generate the analog output signals for relative
humidity (output #1) and for the computed parameter (output #3). In theory, a 12-bit D/A converter
can distinguish between 4,096 values (or counts). This number of counts, together with the span of
the signal (%RH, °C, etc.), determines the resolution of the analog output signal.
Because of the tolerance in the analog components associated with the D/A converter, the number
of counts that are effectively used tends to be less than the theoretical maximum. Typically, only
about 90% of the counts (3,680) may be effectively used.
In addition, the analog output signal may be a partial range. For example, 4…20 mA is a partial
range of 0…20 mA. With a 4…20 mA output signal, the number of useful D/A counts is further
reduced by 20% (1 - 16/20) and only 72% of the count (2,950 counts) may be effectively available.
Taking the example of a 4…20 mA output, the span of the analog signal should not exceed 140 to
150 units (for example –50 to 100°C dew point) to maintain a resolution of 0.1 unit. With analog
signal such as 0…5V or 0…20 mA, a maximum span of 180 units could be used.
The above examples are based on a resolution of 0.05 units as this prevents the analog output
signal from bouncing around by ± 0.1 units.
For the temperature analog output signal, the HygroFlex 3 uses a 16-bit D/A converter. This is
more than sufficient to offer 0.1 resolution for any temperature range and any type of analog signal
available with the HygroFlex 3.
Note: an optional 16-bit D/A converter is available for analog output 1. In that case the computed
parameter is assigned to output 1 and relative humidity to output 3.
