SSP-4 Control and Data Acquisition Program
by Jeff Hopkins Hopkins Phoenix Observatory
June 2006

The SSP-4 can be used manually without needing to be connected to a computer. Connecting to a computer has its advantages, however. The computer software allows finer control of the SSP-4 settings, automatic data acquisition and expanded dynamic range (1 to 9,999 on the SSP-4 as opposed to over 1 to 65,000 with the program).

Installing and Loading the Program

The installation program is called setup_sssp4dataq.exe. This can be downloaded from the Optec web site. Once loaded, click on the icon (see Figure 1) to install the program. The program appears to require at least Windows 95.

Figure 1 Program Installation Icon

Once the program has been installed make a shortcut of the application program and put on the desktop. The application program is called SSP4DATAA.exe (see Figure 2).

Figure 2 Application Program Icon

Using the Program

The SSP-4 Manual has a section on using the software, but it is very misleading. The manual has information about a much lower level of communicating with the SSP-4. The above program is much easier to use and more intuitive.

Clicking on the Application Program Icon (See Figure 2) will load the program and display the window seen in Figure 3.

Note: Make sure the computer's date and time are set correctly as they will be recorded with each observation.

Figure 3 Initial Program Display

Initial Settings

First, if you wish accurate dates and times for the readings, make sure the computer's internal clock is set for the correct date and time. Next, click on the program Setup to display the program Setup drop-down menu as seen in Figure 4.

Figure 4 Program Setup Menu

From the Setup menu:

Time Zone
Use this to set the program for your local time zone. This will allow the program to report Universal Time for the data acquisition.

Com Port
Most likely you will use Com 1.

Connect.
The Messages: window should indicate the computer and SSP-4 are communicating with a Connected message. This must be seen before proceeding. Until the computer has successfully communicated with the SSP-4 the rest cannot be done.

Set Temperature
Unless the ambient temperature is warm, you should enter -40. The temperature of the detector will be seen in the Temperature: window. The display will be red as it cools down to the set temperature value. If -40 cannot obtained due to too warm an ambient temperature, try a setting of -35. Once the temperature has reached the set value the number will turn green and the green light on the SSP-4 will illuminate.

Set up Filters
This allows you to arrange the order of and edit the Filter drop-down menu. Normally nothing needs be done here.

Saving Data

Data that has been acquired can be saved as a text file. You can open a data file that already exists or create a new one. Once created data can be saved to it during the current session and new data added in a future session.
Note: This is not intuitive. To save data you must have a data file open or have created a new one. Then you must Save it and then Clear Data for the data to be put into the Data File.

Open Data File
To save the data select the Open Data File from the File drop-down menu (see Figure 5). Select a current data file or create a new one.

Save
Once the data file has been selected or a new one create any acquired data can be saved.

Clear Data
You can clear the data from the computer display. This will save the data to the data file.

Quit
This will quit the program.

Figure 5 Program File Menu

Data Acquisition Settings

Once the program has been setup and is communicating with the SSP-4 the data acquisition settings can be set (See Figure 6). In Figure 6 all the data acquisition settings drop-down menus are displayed for simplicity. In real life only one menu at a time can be displayed.

Figure 6

Data Acquisition Settings
Note: After the program runs through and displays the data from one set of readings, you can then select a new Object or Filter. You can also change other settings, but it is suggested for a given program star, comparison star, and sky readings, the Gain, Integration and Interval not be changed.

Catalog
Whatever is selected here will be displayed with each set of data. It is unclear as to just what the purpose and meaning of this selection is.

Object
Select the object being measured for this set of data. Typically the comparison star is measure first in both filters, the sky around the comparison star in both filters, Next this is repeated for the program star, then the comparison star again. Three sets of these are then created with the program star bracketed in each set by the comparison star readings. Make sure the Object is set correctly for what is being measured.

Filter (F)
Normally select either the J or H filter, depending on which filter on the SSP-4 is being used.

Gain (SCLE)
While the Manual indicates you can type in values for gain, that seems to not work and you must select one of the three values from the menu. It is recommended to experiment a bit and use the highest gain for all measurements that does not exceed a count of around 65,000.

Note:
The Integration time must be considered too and should also be held constant. The display on the SSP-4 can only go to 9,999. Above that the display will indicate an over range. However, the software program can display up to around a count of 65,000. While it is possible to switch gains between different objects, it is recommended for highest accuracy to keep the gain constant for all measurements during a session for a given set of program data. At HPO we performed some gain linearity measurements and determined the gain is constant to a few tenths of one percent when switching gains. Unless there is a specific reason to switch gains, keeping the gain constant will produce the best accuracy.

Note:
There are two count limits for the SSP-4. There is a voltage-to-frequency converter which has a maximum frequency of around 15 kHz. This relates to a count of 15,000 when using the one second integration. Be sure to keep the counts below 15,000 for one second integrations by adjusting the gain. The second limit is the 16 bit counter which limits the total count to 65,000. To summarize if using a one second integration, keep counts under 15,000. If using a longer integration keep counts under 65,000.

Integration (INT)
This is the gate time for the counter. Again it is indicted in the manual you can make this whatever you wish, but in trying it appears you can only use one of the three selections in the menu. Unless there is a specific reason not to, it is recommended to use a 10 second integration time for all measurements. This will smooth out fluctuations caused by the scintillation of the star light.

Interval
You can select the number of measurements made for a given set of reading. Typically 3 or 4 measurements are used.

Count (COUNTS)
This is a bit confusing, but selecting a trial count will display the results in the messages window and not in the Main Data Window. This can be useful in determining what gain and integration time to use. However, it may be just as easy and provide a record if it is displayed in the Main Data Window. Selecting slow (no idea why this is called "Slow") will set the program for normal data acquisition and display in the Main Data Window.

Start Button
Once the settings are complete and the object is centered in the reticle, the flip mirror is flipped out of the way and the start button selected. The start will change to wait. Do not try to change any setting while the wait is displayed. Doing so can produce strange results. After all the readings have been taken they will be displayed as one line of data in the Main Data Window along with the date and time and settings used. By clicking the Notes button you can add comments for that line of data.

A new line of data will be shown at the top with the last line moved down. If more lines of data are shown than can be displayed the older data will be moved out of the window at the bottom. While there are scroll bars for the window, they are non-functional. While the data out of the window cannot be seen, it is still there and will be saved to the text file.

Note: Don't worry about getting the data listed perfectly. You can always edit the text file after (in case there are bad readings or you forgot to indicate a filter or setting change).

Sample Text File Output

Created 31 October 2006
Modified 31 October 2006

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