Introduction

The 63xx Spectrophotometer is fitted with a bi-directional RS232 interface which allows the unit to be connected to and controlled by a standard IBM compatible personal computer (PC). Transmittance, absorbance, concentration and wavelength can all be read remotely by sending simple character commands. In addition, the 63xx spectrophotometer can receive commands which allow full remote operation, such as wavelength setting and calibration.

This application note details how to control the 63xx spectrophotometer remotely using a PC and standard Windows 3.1 software. Using Windows Terminal^©, the unit can be used to remotely monitor and log readings, as well as for simple scanning or timed assays.

63xx Spectrophotometer Serial Interface

The 63xx has a bi-directional RS232 interface set to:

The 25 way D connector allows a standard one-to-one interconnection lead (Jenway part number 542 009) to be used to connect the 63xx to a PC (a 9 to 25 way adaptor, which is supplied with part number 542 009, may be required for some PCs).

A typical printout obtained from the 63xx is shown below:

======================================
63xx SPECTROPHOTOMETER
OPERATOR .............................
TIME : : DATE / /
======================================
1 100.0 %T 670 nm
2 0.001 ABS 670 nm
3 0.4 mg/l 670 nm (xF = 1000.0)

In addition to the standard printout, transmittance, absorbance, concentration and a voltage proportional to the optical light level can be transmitted by the 63xx in response to a simple ASCII character string command. The remote control commands supported by the 63xx are shown below.

Remote Control Commands

Note <CR> is an ASCII carriage return character.

Using Windows Terminal to Remotely Operate the 63xx Spectrophotometer

The standard interface lead allows the 63xx to be connected to the serial port of a PC. Having established this physical link, Windows Terminal can be used to send and receive data from the 63xx.

Setting Up Windows Terminal

Windows Terminal is located in the Accessories window, which can be opened from within the Windows Program Manager. Start Windows Terminal by double clicking on the Terminal icon.

The RS232 communication parameters must now be set up to match those of the 63xx, as follows.

i Click on the Settings menu option, which will drop down the settings menu.
ii Click on the Communications... menu option, which will open the Communications set up window.
iii Click on the option button to the left of 1200 to set the baud rate to 1200.
iv By clicking on the relevant option buttons set the data bits to 7, the stop bits to 1, parity to odd, flow control to XON/XOFF, and the connector to COM1 or COM2, depending on which connector has been used to connect to the 63xx.
v Click on the option box adjacent to Parity Check to enable parity checking (a cross in the option box indicates that the option is enabled).
vi Click on OK to enter these settings.

Having set the communications parameters, it is then necessary to set the following to format the data received from the 63xx.

i Click on the Settings menu option, which will drop down the settings menu.
ii Click on the Terminal Preferences... menu option, which will open the Terminal Preferences set up window.
iii Enable Inbound CR -> CR/LF by clicking on the Inbound option box. If necessary, disable Outbound CR -> CR/LF. This option sets Terminal to automatically add a line feed character when it receives a carriage return character. This will ensure that each line of text received from the 63xx will appear on a new line (the 63xx only terminates each line with a carriage return character).
iv The remaining options do not require changing from their default settings. If required, Local Echo can be enabled. This will cause characters entered via the keyboard to be displayed on the screen, in addition to the data received from the 63xx. Since typed characters are the commands sent to the 63xx, it is not normally required to echo these back to the screen, in which case Local Echo should be disabled.
v Click on OK to enter these settings.

Terminal is now configured to sent and receive data from the 63xx. The configurations can be saved by using the File drop down menu followed, initially, by the Save As... menu option. Having saved this configuration, the saved file can be subsequently opened which will configure Terminal for operation with the 63xx.

Remote 63xx Operation by Entering Commands Directly

Having connected the 63xx to the PC serial port and set up Terminal, it is now possible to send ASCII commands to the 63xx and receive data from the 63xx.

Since all 63xx commands are capital characters, set the Caps Lock to on.

To read the current transmittance, simply type T and then press the enter key (<-'). The Terminal display will show the transmittance and wavelength, as shown below:

100.0 540

Any of the commands listed can be entered via the keyboard, but will not be displayed unless Local Echo (Settings, Terminal Preferences) is enabled.

Example 1 - Remote Measurement at Fixed Wavelength

The following sequence of commands can be entered which will set the wavelength (540nm), perform a blank calibration and then measure a sample.

i Type G540(<-'). The 63xx will go to 540nm.
ii Type SC(<-'). This will close a shutter on the 6300 which blocks light, thus enabling a dark calibration to be performed.
iii Type Z(<-'). This calibrates the 6300 to zero transmittance.
iv Type SO(<-'). This opens the shutter, which allows monochromatic light to enter the sample chamber.
v Place the sample blank (deionised water) into the sample chamber. Type Z(<-'). This calibrates the 63xx to zero absorbance (100% transmission).
vi Sample readings can now be down loaded by typing T(<-') (to read transmission), A(<-') (to read absorbance) or C(<-') (to read concentration). Concentration is reported as absorbance multiplied by a factor, which can also be set remotely, for example to 1000 by typing F1000(<-').

Example 2 - Combining Commands

Windows Terminal allows text contained in a standard text file (created by Windows Notepad, for example) to be transmitted to the 63xx one line at a time (that is, one command at a time) at a fixed interval (the time interval between commands). This allows commands to be combined and transmitted as a single operation. This example describes how to perform a blank calibration at 540nm.

i Open Windows Notepad and enter the following lines of text:

G540
SC
Z
SO
Z

ii Save this file as ZEROCAL.TXT.
iii Open Windows Terminal, and load the configuration file described in "Setting up Windows Terminal" to prepare to communicate with the 63xx. Note that applications can be minimized and reopened, which allows switching between Notepad and Terminal without re-configuring Terminal.
iv Click on the Settings menu option, which will drop down the settings menu.
v Click on the Text Transfers... menu option, which will open the Text Transfers set up window.
vi Click on the option button to the left of Line at a Time to enable text transfers one line (one 63xx command) at a time.
vii Enter a Delay Between Lines in tenths of a second for the delay between commands. It is recommended that a minimum of two seconds (20 tenths) is allowed for the 63xx signal levels to stabilize between commands.
viii Click on OK to enter these settings.
ix To transfer the calibration file, click on the Transfers menu option, which will drop down the transfers menu.
x Click on the Send Text File... menu option. This will open a file selection window.
xi Under File Name: enter or select the file created in step ii (ZEROCAL.TXT).
xii Click on OK. This will send the file to the 63xx which will execute the commands sent. Text transfers can be paused or stopped by clicking on the appropriate buttons whilst Terminal is transferring the text file.

Example 3 - Transferring Data Received from the 63xx to Other Applications

Windows Terminal does not allow data captured to be saved directly, but it can easily be copied to the clipboard and subsequently pasted into other applications. This example describes how to copy 63xx data into Notepad, which can then be edited and saved. If copying data into some Spread Sheet applications, which requires data to be placed into separate cells, it may be necessary to separate readings (transmittance, absorbance or concentration) from wavelength by a character that is interpreted by the Spread Sheet package. This is usually a TAB character, which is used by the 63xx to separate reading and wavelength. However, Terminal replaces the TAB character with spaces when the data is displayed. Therefore, if the Spread Sheet requires a TAB character between cells, then this must be entered manually using Notepad if pasting the data into the Spread Sheet.

i Open Windows Terminal and configure for operation with the 63xx.
ii Receive the data from the 63xx to be copied.
iii Select the data by clicking and dragging over the required text, or by using Select All from within the Edit menu.
iv Copy the selected text to the Windows Clipboard by clicking on the Copy menu option from within the Edit menu option.
v Switch to the Program Manager window (ALT-TAB) and open Windows Notepad.
vi From within Notepad, click on the Edit menu option and then click on the Paste menu option. This will copy the text received from the 63xx onto the Notepad.
vii Using Notepad, edit and save the copied data as required. This file can then be loaded into other applications, such as Microsoft Works.

Example 4 - Time Related Monitoring

By creating a text file which contains a large number of command lines which take readings from the 63xx and then transferring the commands at a fixed time interval, it is possible to continuously monitor the 63xx, or to make time related measurements. This example illustrates how to read a sample absorbance every 10 seconds for one hour.

i Create a text file using Windows Notepad which consists of 600 lines, each with just an A character on each line (use copy and paste), as shown below:

A
A
A
A
.
.
A
A

ii Open Windows Terminal and configure for operation with the 63xx.
iii Select the required wavelength on the 63xx and calibrate as required.
iv Using the method described in Example 2 - Combining Commands, set the Delay Between Lines (Settings, Text Transfers...) to 100 tenths of a second (10 seconds, the maximum delay is 25.5 seconds).
v When ready to start measuring, transfer the file created in (i) using Transfers, Send Text File... Note that Windows Terminal can be minimized whilst it is transferring the command file to allow other applications to be used.
vi Once the readings have been captured, they can be copied into Notepad and saved as a text file, as described in Example 3 - Transferring Data Received from the 63xx to Other Applications. This file can then be incorporated into most Spread Sheet or Word Processing packages.

Example 5 - Using the 63xx for Simple Scanning

The 63xx can be used for simple scanning at slow speeds by transferring a text file which steps through the required wavelength range. This example shows how to scan between 500nm and 550nm at 5nm intervals. During the process, several data points are collected, which are conveniently interpreted using a Spread Sheet package.

Four stages are required to perform a scan: dark level measurement, baseline scan, sample scan and absorbance calculation. It is assumed that Windows Terminal, Notepad, and the Spread Sheet have been opened and set up as described in previous examples.

Stage 1 - Dark Level Measurement.

i Send the following commands to the 63xx:

SC(<-')
V(<-')

The 63xx will respond with a voltage and wavelength, for example:

1234.5 540

ii Copy this data to a text file (using Notepad) and save as DARK.TXT
iiiClear the data received in Terminal using Clear Buffer under the Edit menu.

Stage 2 - Base Line Measurement

i Place a sample blank (deionised water) in the 6300 sample chamber and set the wavelength to 500nm (the start wavelength).
ii Create a text file (Notepad) which contains the following commands:

G500
V
G505
V
G510
V
G515
V
G520
V
G525
V
G530
V
G535
V
G540
V
G545
V
G550

iii Using Text Transfers... send this file to the 63xx with a delay between lines of 20 tenths of a second.
iv The 63xx will respond by transmitting the voltage proportional to monochromatic light level at each wavelength, as illustrated below:

200.00 500
210.00 505
220.00 510
230.00 515
240.00 520
250.00 525
260.00 530
270.00 535
280.00 540
290.00 545
300.00 550

v Copy this data to a text file (using Notepad) and save as BASE.TXT
vi Clear the data received in Terminal using Clear Buffer under the Edit menu.

Stage 3 - Sample Measurement

i Place the sample in the 63xx sample chamber and set the wavelength to 500nm (the start wavelength).
ii Transfer the command text file created in Stage 2 ii to scan the sample. The 63xx will respond by transferring readings as illustrated below:

10.00 500
10.00 505
20.00 510
30.00 515
200.00 520
210.00 525
180.00 530
100.00 535
80.00 540
20.00 545
20.00 550

iii Copy this data to a text file (using Notepad) and save as SAMPLE.TXT
iv Clear the data received in Terminal using Clear Buffer under the Edit menu.

Stage 4 - Scan Calculation

Having captured the base line and sample scans into text files, it is now possible to calculate the transmission, absorbance or concentration at each wavelength. The relationships for calculating these parameters from the voltages output by the 63xx are shown below.

Transmission = (Sample Voltage at l - Dark Voltage) ÷ (Base Line Voltage at l - Dark Voltage)

% Transmission = Transmission x 100

Absorbance = log ( 1 ÷ Transmission)

Concentration = Factor x Absorbance 

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