Care should be taken to ensure that the switches are fully
set to either the 0 or 1 position, and that these provide the correct baud rate e.g. 9600,
Mains frequency e.g. 50 or 60hz and address.
As part of a maintenance program all switches should be
moved and reset to their original positions on a 12 monthly basis to help offset
contamination. Contamination may occur during shipment and so may not have been present
during final test.
Unused inputs
All unused inputs should be set to a defined input. This is
best achieved by shorting all poles on a given channel for each unused channel. This helps
alleviate floating inputs and range hunting on certain scanner modules.
Analog inputs
All analog inputs should have the guard terminal connected
as per the connection details.
All thermocouple inputs should follow the guidelines laid
out in the manual.
All 4-20ma current transducers connected to Datascan should
have an external precision 62 Ohm resistor fitted across the High and Low terminal. This
enables the scanner to measure the voltage developed across it and convert it internally
to a current reading.
Analog outputs
The 7050 scanner module requires an external 24 Volt DC
Power Supply when any of the outputs are used in current mode. This is connected to the
scanner module directly, and is in addition to the power provided to it via the processor
module.
Common mode problems with non
isolated modules
If the unit you are using is a non isolated scanner i.e.
7X20 or 7X21 a maximum of 12 Volts potential between any two channels is the maximum
permissible. This can be a problem in installations where the earth levels of the
transducers, particularly 4-20ma, or peripheral equipment are at a higher potential than
the earth level used by the Datascan system.
If the common mode performance of the system is exceeded
Datascan will behave in an unpredictable fashion causing spurious readings and unexpected
results.
The problem is not generally with one earth, but with many
that may force the inputs to be out of the common mode range. If a large number scanners
are connected to a processor the problem channel could be on a totally different module to
the one giving the spurious readings.
All inputs should be maintained relative to one common
Earth which can be referenced to the Datascan Earth.
Network termination
When using the RS485 network facilities of Datascan, both
ends of the network should be terminated with the terminators supplied. These stop
reflections on the network and ensure reliable data transmission and integrity.
Channel Addressing
Each scanner module on a Datascan system must have a unique
address.
7200 series and 7041 modules only support channel addresses
in the range 1-256.
16 Channel scanner modules i.e. 7X20/21 can only be placed
on a 16 channel boundary.
A maximum of 32 processing units (nodes) can be supported
on each network. The 7011, 7041 modules all count as 1 node.
Troubleshooting Using Windows
Terminal Emulator
A simple way to test your Datascan hardware when problems
are encountered is to use the Terminal Emulator supplied with Windows. This allows you to
talk directly to Datascan using ASCII software commands and therefore suppress any
possible problems related to the host software used.
The Windows Terminal Emulator can be found in the
Accessories program group.
Before sending software commands to the processor, you need
to configure the terminal emulator so that it can successfully communicate with Datascan.
Configuring Windows Terminal
You will find in the Settings Menu all the following
configuration options.
In each of the following Dialog Boxes, the selected options
are the ones required to get your system going.
RS232 Communication Configuration.
Defines the Communications: hardware, data transfer speed,
and protocol to use.
Baud Rate : Choose the appropriate rate according to the
DIP switch setting on the processor to which your PC is connected, i.e. 9,600 or 19,200
Baud.
Terminal Emulation
Defines the type of terminal to be emulated
Terminal Preferences
Sets the various options referring to the terminal i.e.
Line Feed (LF), Carriage Return (CR) etc...
NB: Local Echo : Ctrl + E is the first
command you need to send to Datascan to set the serial communications to a known mode.
Talking To Datascan
Note : To validate any command you need to press the Return
key.
Re-setting the RS232 Datascan Communications.
Press Ctrl+E This command forces the Datascan unit
to terminate whatever it is doing on the RS232 line and sets the RS232 protocol to Echo On
and No handshake. The Echo enables the user to verify the characters entered at the
keyboard.
Is My Terminal / Datascan Communicating?
Press any key: You should see the corresponding character
on the screen and the RS232 LED on the Datascan Measurement processor flash.
Press the Return key A ' $ ' or ' * ' prompt should appear
on the screen.
Type 'iv' then Return: Datascan should give you the
firmware version of the PROM fitted in the unit with either a ' $ ' or a ' * ' prompt.
At this point if Datascan is not responding correctly you
need to check that all the above options have been correctly selected and that your RS232
cable is wired properly and works. Having done that if Datascan still fails to respond
then contact your local dealer for support.
Reset Datascan
Type the following commands ending each with a RETURN.
TC This is to gain control of the Datascan system, the
reply prompt should be a '$'.
TR This command resets the Datascan System, clears any
configurations stored in memory and leaves the processor in listener mode. The reply
prompt should be a '*'.
TC This command puts the Measurement Processor into
controller mode, the reply prompt should be a '$'.
The following shows an example of the Terminal Screen after
these commands have been sent.
Configuring The Datascan System
Simple configuration of the Datascan System is done using
two commands.
CT to set one or a group of channel to a certain type.
CS to specify the range and speed/resolution of
measurements taken.
To set channel 1 to 8 with milli-volt voltage, 16 bits,
auto-range send the following commands:
CT1,8,2 ' sets ch 1 to 8 to milli-volt input type
CS1,8,0,1 ' specify auto-range and 16 bit.
Refer to the software commands section of the Datascan
Technical Reference Manual for more details.
Note : You can perform sensible measurements without any
inputs connected to the unit by measuring the on board thermistor used to measure the cold
junction of thermocouples. By setting the input type to CJC, type number 13, Datascan
measures the ambient temperature where the module's located. This facility is very useful
to verify the unit.
Getting Results from Datascan
There are two ways to read a single channel or group of
channels
One-off report of data
You need to set standard report format, start scanning the
channels you want and then request the data. This is done by the following set of commands
(example for the 8 first channels):
RM 0 ‘ sets standard report format
SC1,8 ‘ starts scanning channel 1 to 8
RL1,8 ‘ requests the reading of channel 1 to 8
This will give the first 8 channel results in ASCII
characters to the screen.
As an example the screen below shows the configuration and
report of channels 1 to 4.
Continuous report of data or monitor page
The following explain how to configure and run simple
monitor for 16 channels.
You need to set the monitor page, start scanning the
channels you want, and then run the monitor page. This is done by the following set of
commands:
RM 0 ‘ sets standard report mode.
MA 1,16,1 ‘ add channel 1 to 16 to display in monitor
page 1.
MF0,*1 ‘ set display format to VT52 terminal mode.
SC1,16 ’ starts scanning channel f to l
MR 1 ’ run monitor page 1
Press ESC to exit the monitor page. You should get a prompt
again.
Example of a Continuous report of data or monitor page
You can set-up to 10 pages of monitoring data with up to 16
channels of each of these page. Follows a set of commands to set channel 1 to 16 to
monitor page 1.
Commands sent:
CT1,2,1 ' sets ch1 to 2 to microvolt input
CS1,2,1,1 ' sets ch1 to 2 to 20mV range, 16 bit
CT3,16,13 ' sets ch 3 to 16 to CJC inputs
CS3,16,0,0 ' sets ch 3 to 16 to autorange, 14bit
SC1,16 ' start scanning ch 1 to 16
RM1 ' report mode 1
MA1,16,1 ' add ch 1 to 16 to monitor page 1
MF0,*1 ' defines VT52 monitor format
..... ' Optional commands
MR1 ' run monitor page 1
Optional commands :
MT Example ,1 ' sets 'Example' as title of monitor page
CL1,1,Boiler1 ' sets 'Boiler1' label to channel 1
CL1,2,Boiler2 ' sets 'Boiler2' label to channel 2
CL1,3,AmbientT ' sets 'AmbientT' label to channel 3
CU1,2,4 ' sets uV unit for ch 1 to 2
CU3,16,17 ' sets 'C unit for ch 3 to 16
CA1,1,10000,1000 ' Sets a High alarm of 10,000 (AH tag) and
a Low Alarm (AL tag) of 1000 on ch1
FT 10.30.00 ' sets time
