ROTRONIC HygroLab - Manual (Page 37)

IN-E-HyLab-V4_11
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
Instruction Manual
Document Type
HygroLab bench top indicator version 4:
instruction manual
Document title
Page 37 of 51
© 2006; Rotronic AG IN-E-HyLab-V4_11
The accuracy of the dew point conversion is less than the accuracy that is normally achieved with a
chilled mirror instrument. This is especially true at low dew point values (dew point depression of
more than -40…-50
°C) and at low temperatures. In many applications, repeatability is more critical
than accuracy. Repeatability of the dew point conversion is typically 1/3 of the accuracy shown
above. Using a dew point conversion permits to measure conditions that cannot be measured with
a chilled mirror instrument. Typically, the measuring head of a chilled mirror instrument is limited to
a maximum of 70
°C and, therefore, cannot measure a dew point temperature above 70°C. In
addition to the ability to operate at high temperature, the relative humidity probe offers significant
advantages for industrial applications: less maintenance and higher tolerance to contaminants, no
sampling system, no uncertainty between dew and frost and better response to fast changing
conditions.
16 ASCII communications protocol
The HygroLab indicator is compatible with two different communications protocols: ASCII and
HW4. When interrogated, the HygroLab automatically recognizes which protocol is being used and
does not require a manual configuration of its serial settings.
The following describes the ASCII communications protocol. This information is provided for users
who for any reason are planning on using their own software.
Connections with a PC COM port
The exchange of data requires 3 wires: TXD (transmit), RXD (receive) and SG (signal ground).
When the ROTRONIC device requires power from the COM port (example: MOK-WIN probe
calibration cable), the RTS and DTR wires are also used.
Settings required by the ASCII communications protocol
The ASCII communications protocol uses only 7-bit ASCII characters (ASCII 32 to 127).
Parity :
even
Data bits : 7
Stop bits : 1
Use these settings to configure a third-party software used to communicate with the HygroLab (see
ASCII commands provided in this manual). Also use these settings to configure a device server
(connection of a serial device to an Ethernet LAN). Set flow control to none and, if necessary, force
incoming data to 7-bit ASCII.
Models with optional Ethernet interface: the internal Ethernet module should be re-configured to
use these settings. Detailed instructions are provided separately in document IN-E-TCPIP-Conf_11
(available in PDF format).
Baud rate
Compatibility with the ASCII protocol requires the 19200 Baud rate (factory default).
IMPORTANT: Please note that all devices connected to an RS-485 multi-drop should use the same
baud rate in order to communicate.