dataTaker - Data Loggers, Powerful and Flexible Data Acquisition & Data Logging Systems

The NETWORK Interface

Up to 32 dataTaker 500/600 series loggers can be connected into a network, where individual loggers are linked together via their NETWORK interfaces.

Note :  The dataTaker 50 does not provide networking capability.

The network for dataTaker 500/600 series loggers can be up to 1000 meters (1100 yards) in length. The maximum length of the network cabling is limited only by the attenuation of the communications signals. Therefore data quality cable should be used where long distance networks are to be established, while simple telephone cable is sufficient for short distance networks.

The NETWORK interface of the dataTaker 500/600 series loggers is implemented as a RS485 serial interface, and communicates at a fixed 1200 baud. The interface is not electrically isolated, and is powered from the logger.

There are no master or slave units in a dataTaker network. The host connects to the network via the RS232 COMMS of any dataTaker in the network. All dataTakers in a network have equal status, and each is identified by its unique network address.

A proprietary clash detection and error correcting protocol operates to ensure error free transmission on the network. However this can slow network communications if a number of loggers are trying to communicate simultaneously. The network should be managed such that only one logger is communicating at any one time.

Wiring a dataTaker Network 

The NETWORK interface has screw terminals located beside the 9 pin D connector for the RS232 COMMS interface. The screw terminals are labelled NET + and NETñ.

 

 

Figure 18 ñ Network Cabling Schematic for dataTaker 500/600 Series Loggers

 

Figure 19 ñ Network Terminals for dataTaker 500/600 Series Loggers

A dataTaker network is established by connecting the positive terminals of each logger in the network together, and connecting the negative terminals of each logger together.

It is recommended that shielded network cables be used. The shield continuity between successive dataTakers is maintained via the GND terminals of the loggers. The network cable shields should be grounded at one point only, and care should be taken that the shield is not grounded at any other point.

Network Address 

Each dataTaker in a network must have a unique network address. The network address is set via the Network Address switches of the DIP switch. The DIP switch is located behind the memory card connector, under the battery cover.

The Network Address switch settings of the DIP switch for the 32 available addresses are illustrated in Figure 20 below.

The use of the network address when sending commands to a group of dataTakers that are connected in a network is discussed in the Section III ñ dataTaker Networks.

 

 

Figure 20 ñ Setting the Network Address of the dataTaker 500/600 Series Loggers

The Network and Modems

The dataTaker network can be extended by modems or radio modems that are able to operate at 1200 baud and can automatically 'turn around' (change direction of data transfer). This is an important issue for radio modems, where changing from transmit mode to receive mode can take as long as 500 mS.

The dataTaker network turn around time is defined by the Parameter7 command in increments of 14 seconds. For example the command

P7=22

sets the turnaround time to 300 seconds.

The dataTaker does not issue an electrical signal or a message preamble to indicate turn around. The modem must detect when the dataTaker is sending data, and rapidly switch to the transmit mode.

Networking and Low Power Mode

When the dataTaker is asleep, the logger will not wake when network activity begins. To ensure proper operation of loggers in a network, the following should be done

the loggers can be kept awake by setting Parameter15=2

the Wake terminals of all networked loggers can be linked together such that when one logger wakes they all wake

diode couple the negative network wire between loggers to the Wake terminal of each logger. Any activity on the negative network line will then wake all loggers. The diode is necessary to prevent the 10 Hz signal which is output from the Wake terminal while the logger is awake, from entering the network.

dataTaker 50 Address

The dataTaker 50 can be assigned an address, which provides a form of password security to the logger.

 

 

Figure 21 ñ Setting the Address of the dataTaker 50

 

The address can be set in the range of 0 to 15 by the four Address switches of the DIP switch under the top cover of the logger.

The use of the dataTaker 50 address when sending commands is the same as when commanding a network of dataTaker 500/600 series loggers. This is discussed in the Section III ñ dataTaker Networks.

Page Content


Home

Title and Waranty

Go to: Section 2 | Section 3

Section 1


Construction of the dataTaker 50

Construction of the dataTaker 500 600

Construction of the CEM

Getting Started

 

Section 2


Interfacing

Powering the dataTaker

Powering Sensors from the dataTaker

The Serial Interfaces

The RS232 COMMS Serial Interface

The NETWORK Interface

Analog Process

Connect Analog

Analog Chns

Measuring Low Level Voltages

Measuring High Level Voltages

Measuring Currents

Measuring 4-20mA Current Loops

Measuring Resistance

Measuring Frequency and Period

Measuring Analog Logic State

Measuring Temperature

Measuring Temperature with Thermocouples

Measuring Temperature with RTDs

Measuring Temperature with IC Temperature Sensors

Measuring Temperature with Thermistors

Measuring Bridges and Strain Gauges

Measuring Vibrating Wire Strain Gauges

The Digital Input Channels

Monitoring Digital State

The Low Speed Counters

The Phase Encoder Counter

The High Speed Counters

The Digital Output Channels

The Channel Expansion Module

Installing The Panel Mount Display

 

Section 3


Programming the dataTaker

Communication Protocols and Commands

Entering Commands and Programs

Format of Returned Data

Specifying Channels

The Analog Input Channels

The Digital Input Channels

The Counter Channels

The Digital Output Channels

The Real Time Clock

The Internal Channels

Channel Options

Schedules

Alarms

Scaling Data - Polynomials, Spans and Functions

CVs Calcs and Histogram

Logging Data to Memory

Programming from Memory Cards

STATUS RESET TEST

Switches and Parameters

Networking

Writing Programs

Keypad and Display

Error Mess Text

Appendix A - ASCII

Appendix B - ADC Timing