Michell Instruments Easidew Online User Manual

Easidew Online User’s Manual
Michell Instruments 39
OPERATION
3.6 Monitor – Reading the Displayed Value Using Modbus RTU Over RS232
It is possible to communicate with the online monitor using Modbus RTU over RS232.
The monitor has a three pin serial port connection on the back – the required cable can
be supplied by Michell (see Appendix B for set-up information).
To read the value displayed on the monitor a byte array must be created, containing
the following bytes:
Instrument
Address
Command
Reg
Address
High
Reg
Address
Low
Number
of Reg
High
Number
of Reg
Low
LRC CRC
0x01 0x04 0x00 0x00 0x00 0x01 0x31 0xCA
Send this to the instrument with the correct delays between characters:
Baud Rate (bps) Min Delay (ms) Max Delay (ms)
1200 9.17 13.76
2400 4.59 6.88
4800 2.30 3.44
9600 1.15 1.72
19200 0.57 0.86
After a few seconds the instrument will send back the following response:
Instrument
Address
Command
Number of
bytes
Display
High
Display
Low
LRC CRC
0x01 0x03 0x02 0x00 0x67 (Varies) (Varies)
Data MSB * 256 + Data LSB = 0 *256 + 103 = 103
This code, written in c, can be used to convert the 103 into a real dew-point value or
10.3:
fl oat ConvertToReal(int Value) //convert dew-point value to real dew-point result
{fl oat result; //declaration
if (Value > 32767) Value=(Value-65536); //convert to negative number
result = (fl oat)(Value/10.0); //divide number by 10 to convert to fl oat
return result; //return real value}

Michell Instruments Easidew Online Specifications

General

Brand	Michell Instruments
Model	Easidew Online
Category	Measuring Instruments
Language	English

Summary

Safety Information

Electrical Safety Precautions

Ensures safe operation and electrical integrity of the instrument and accessories.

Pressure Safety Guidelines

Details safe working pressure limits to prevent instrument damage or failure.

Toxic Materials Handling

Information on minimizing exposure to hazardous substances during maintenance.

Repair and Maintenance Procedures

Guidelines for maintaining the instrument, including authorized service.

Calibration Recommendations

Recommended calibration interval and procedure for maintaining accuracy.

Safety Conformity Standards

States compliance with relevant EU and US safety directives.

1 INTRODUCTION

2 INSTALLATION

2.8 Electrical Connections

Overview of all electrical connections for the Easidew Online system.

2.14 Signal Output Connections

Details connections for alarm outputs and re-transmitted signals on the monitor.

3 OPERATION

3.2 & 3.2.1 Preparation and First Time Operation

Steps to prepare the instrument for operation and conduct the initial start-up.

3.3 & 3.3.1 System Alarms and Default Logic

Describes the two alarm outputs and their default switching logic settings.

3.3.3 Alarm Level Set-Up

Guide for configuring the individual alarm set-point levels for the instrument.

3.4 & 3.4.1 Temperature Range and Defaults

Explains default temperature units (°Cdp) and associated span settings.

3.4.2 Span and Unit Settings

Procedure for changing the span limits and temperature units (°C to °F).

3.4.3 Alarm Set-Point Limit Configuration

Setting alarm limits, particularly after re-configuring the instrument's range.

3.4.4 Scale Units to ppm, Set-Up

Guide to re-configure the monitor to display dew point in parts per million by volume.

3.5 Digital Communication Parameters Set-Up

3.6 Monitor – Reading the Displayed Value Using Modbus RTU Over RS232

4 GOOD MEASUREMENT PRACTICE

4.2 & 4.2.1 Maintenance and Monitor Cleaning

4.3 Fault Conditions

Lists common error messages, their causes, and recommended actions.

Appendix A Technical Specifications

Monitor Performance and Specifications

Transmitter Performance and Specifications