• the bed speed of the “Classic Shadow Shield Whole Body Counter,”
• the carriage speed of the “Do-It-Yourself Lay-Down Whole Body Counter,”
• the vertical speed of the detector for the “HPGe Waste Analyzer,”
• the vertical speed of the detector for the “Quicky,” Model IV, the “dual detector Quicky,”
• the vertical speed of the detector for the “Quicky,” Model V, the “HPGe Quicky,”
• the rotational speed of the “BRC Waste Analyzer” and
• the rotational speed of the “HPGe Waste Analyzer.”

This portion of the Instruction Manual does not apply to “Quicky,” Models I, II, III, or VI Counters, since they have no moving parts.

Figure 17-1, This is the "HELGE" Main Menu with “Calibration” highlighted.

To enter the program select the “Parameters Modification” option from the Main Menu, shown in Figure 17-1, above. To do this:

• press “4” on the keyboard, or
• move the highlighted bar to the fourth line with the “arrow” keys, then press the <ENTERƒ> key.

Figure 17-2, This is the Calibration Menu with “Speed Calibration” highlighted.

Normally, there are four calibration options, as shown in Figure 17-2, above, however, if you are using the “BRC” software, you will find a fifth option, as shown in Figure 17-3, below. Regardless of which calibration menu you are using, you would use Option 3, “Speed Calibration.” This will bring you to the opening screen for the speed calibrations, Figure 17-4, below. But first let us look at some fundamentals about speed (velocity) calibrations.

Figure 17-3, This is the Calibration Menu which is obtained when you are working with a “BRC Waste Analyzer.”

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17.1. The Mathematics of Speed Calibrations

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The purpose of this chapter is to provide an easy method for calibrating the velocity of the carriage, bed, or vertically traveling detector in centimeters per second as a function of the counting time in seconds. The motor speed control unit, which controls the motor speed, may be operated:

• in the “AUTO” mode, where the motor speed is controlled by the computer, or
• in the “MANUAL” mode, where the speed is controlled manually by the “dial setting” of the external manual control.

The purpose of this program is to determine the rate at which the device travels as a function of the two methods of control mentioned above. We shall be using the “AUTO” method in these examples, but the principle remains the same for the “MANUAL” method.

17.1.1. Basis of the Program

The basic algorithm of the program is very familiar, since it is used every day when walking or driving a car: the distance traveled is the product of the rate times the time, or

      Distance = Rate * Time

Since the carriage (or bed) of the “Classic Shadow Shield Whole Body Counter” or the “Do-It-Yourself Lay-Down Whole Body Counter” always travels exactly the same distance in going from one end to the other, this value is a known constant. In fact, before you start the program, you must measure this distance so that you may enter it into the program when it is requested. For example, the total carriage travel distance of typical counter was found to be 71-15/16, or 71.9375 inches or 182.72 centimeters. Since we can measure the travel time required, the computer can calculate the speed and store it for later use in determining the equation of speed versus one of the above parameters. Please remember that all data are stored in the “cgs” system, that is, all dimensions are stored in centimeters, all weights in grams, and all times are in seconds, except in the ICRP30 calculations, where the time is referenced in days.

Table 17-1, below, shows the output from a “DIYS” calibration. The user never sees this table because the program calculates the equation of the speed versus voltage from the analog-to-digital converter without listing the individual values. Obviously, the first row contains the date of the calibrations. The numbers in the remaining rows give the voltage from the digital-to-analog converter, the velocity in cm/sec, and the product of the two in volt-cm/sec. The product is used in the least squares regression calculation. A complete discussion of the least squares method is contained in Chapter 36.

The same mathematics applies to the calculation of the rotational speed of the Waste Analyzers. The major difference is that we are working in revolutions per second. Since the turntable always makes one revolution, we shall calculate revolutions per second.

Table 17-1, This shows the results of the speed calibration of a “Do-It-Yourself Lay Down Whole Body Counter.” The first column is the voltage from the DAC, the second is the velocity, cm/sec, and the third is the product, volt-cm/sec. The data are now ready for the regression analysis by the “Least Squares” method.
1993/10/26
1.500000	0.391569	0.587353
2.000000	0.539357	1.078714
2.500000	0.689225	1.723063
3.000000	0.843845	2.531536
3.500000	0.997132	3.489961
4.000000	1.150051	4.600204
4.500000	1.300535	5.852407
5.000000	1.451283	7.256414
5.500000	1.602581	8.814197
6.000000	1.748055	10.488329
6.500000	1.894817	12.316308
7.000000	2.035214	14.246496
7.500000	2.175810	16.318577
8.000000	2.315887	18.527096
8.500000	2.452964	20.850197
9.000000	2.586356	23.277200
9.500000	2.711023	25.754719
10.000000	2.830117	28.301175
END-DOWN
1.250000	0.050969	0.063711
1.750000	0.194810	0.340918
2.250000	0.341425	0.768206
2.750000	0.488901	1.344477
3.250000	0.639355	2.077905
3.750000	0.791977	2.969915
4.250000	0.941117	3.999749
4.750000	1.087071	5.163586
5.250000	1.240654	6.513432
5.750000	1.388987	7.986678
6.250000	1.528605	9.553783
6.750000	1.669009	11.265814
7.250000	1.811970	13.136782
7.750000	1.954928	15.150692
8.250000	2.091681	17.256366
8.750000	2.224298	19.462610
9.250000	2.349673	21.734476
9.750000	2.476106	24.142029

The instructions for using the program are very simple and are contained within the program. The next section of this chapter shows the various screens obtained during the calibration of the carriage speed of a “Do-It-Yourself Whole Body Counter.” These screens will apply equally well to the “Classic Shadow Shield Whole Body Counter,” and to the vertical detector movements of the “Quicky,” Models IV and V, and to the “HPGe Waste Analyzer.”

17.2. Linear Speed Calibrations

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When you choose Option 3 from the “Calibration” sub-menu, you will receive the screen shown in Figure 17-4, below. This is merely an information screen.

Figure 17-4, This is the opening screen of the Linear Speed Calibration program.

Press any key to continue. This will bring you to Figure 17-5, shown below.

Figure 17-5, This first screen asks if you wish to review previous data in text format.

17.2.1. Review of Previous Data

If you wish to see a coefficients of the existing speed calibration, answer “Y” and press the <ENTERƒ> key. Figure 17-6, below, shows these coefficients.

Figure 17-6, These are the results from the previous linear calibration.

The slope has units of centimeters per second per volt and the intercept has units of centimeters per second. Note that the correlation coefficients are very good, as you will see from Figure 17-7. The curve is quite linear. The equations may be obtained using only three data points, however, and suggest that if you have plenty of time to perform this calibration, that you start at 1.0 volt and continue to 10.0 volts in steps of 0.5 or 1 volt. This will give you a very good linear line.

Figure 17-7, This is graph of the previous calibration. L-R Equation: Speed = -0.29357 + 0.2884*Voltage from DAC, Correlation = 0.999451 R-L Equation: Speed = -0.01765 + 0.2902*Voltage from DAC, Correlation = 0.999143

After you have finished viewing the graph, press any key and you will be presented with the screen shown in Figure 17-8, below, asking if you wish to save these data. Since this is a review of a previous calibration, you would normally answer “N” to this question.

Figure 17-8, Each time you look at the results, the computer asks if you wish to save them to disk.

However, if you did answer “Y”, then you may be asked to enter your password (only if your System Manager has elected to require a password for this program), as shown in Figure 17-9, below, which authorizes you to make these kinds of changes.

Figure 17-9, Since we have decided to save the data, we must enter the password.

Table 17-2, below, gives the final output of the linear speed calibration. You will not see these data, either, just the same information shown in Figure 17-6.

Table 17-2 This is the final output from the linear speed calibration. "D" stands for the values for the "Down" direction and "U" stands for the values for the "Up" direction
1994/05/17
Rpm Intercept :	-0.081539400000
Rpm Slope :	0.222521500000
RPM D/A Range :	7
D Linear Intercept	-0.038091312
D Linear Slope	-0.005096710176
U Linear Intercept	-0.0050967
U Linear Slope	0.0386533
Linear D/A Range	4
Linear Distance, cm	180.0000

We are now ready to find out how to obtain new data.

17.2.2. Obtaining New Speed Calibration Data

Figure 17-10, below, asks two very important questions:

• Full length bed travel and
• Run speed calibration fully automatically (Y/N)

It is important to know the total length of travel of the device (bed, carriage, or detector) so that the velocity calculations may be done correctly. We suggest that you mark the starting point of the device, make it travel to its ultimate distance in the opposite direction, and measure the distance to the reference point from the starting point. Remember, if you are working in inches, the program will automatically convert it to centimeters.

Figure 17-10, We are ready to start a new linear speed calibration. We are also choosing to do an automatic calibration.

The second major question “Run speed calibration fully automatically (Y/N),” will allow you to start the calibration then leave it, or let the device move a short distance and enter this distance for each of the measurements.

The advantage of automatic operation is that everything is automatic. Another advantage is that since the device is traveling the full length every time, the accuracy of the measurements will be very good. The disadvantage is that if you start the voltage around 1.0 volt, and if the voltage increment is small, then the entire process will take quite a bit of time, several hours, for example.

The advantage of manual operation lies in the fact that you can allow the device to move a relatively short distance for some or all of the runs. The advantage of this is the savings of time. The disadvantage is that the accuracy and precision of the final results are not nearly as good as the automatic operation. We recommend automatic operation whenever possible.

17.2.2.1. Automatic Operation

The speed of the detector is controlled by the computer. A low direct current voltage is sent from the digital-to-analog converter, located inside the computer, to the motor speed controller which then converts this to a 0 - 90 volt direct current signal which powers the motor. For example, a motor voltage of 90 volts will move the “DIYS” carriage from one end to the other in less than 2 minutes, while a motor voltage of 10 volts will send it the same distance in about 45 minutes. Don’t confuse motor voltage with DAC voltage.

For this demonstration we used voltages from the digital-to-analog converter ranging from 5.0 volts to 10.0 volts. (It was not really necessary to type the “+” sign in front of the numbers.) The voltage increment was set to 1.0 volt per step. See Figure 17-11, above.

Figure 17-11, We have told the analog-to-digital converter that we want a range of 5.0 to 10.0 volts with a 1.0 volt step between runs.

When the voltage increment has been entered, the calibration starts, as shown in Figure 17-12, on the top of the next page. Note that the voltage is “-5.0” volts. The minus sign signifies that the carriage is going to the left. We have followed standard graphing nomenclature in choosing the polarity of voltages. Just as in an X-Y graph the “X” axis is positive to the right of the “0,0” point and negative to the left, so will the device direction be:

• positive send the device to the right and negative sends it to the left,
• positive sends the device up and negative sends it down.

All rotating devices go in the same direction, so polarity is not important.

The next six figures show the progression of the data collection for the conditions described in Figure 17-11, above. We have chosen to “waste some paper” by showing the six different figures so the user will be aware that the polarity will change with every other run.

Figure 17-12, above, shows the beginning of the data collection. Note the “-” sign in front of the “5.00” signifying that the carriage is going from the right to the left, as we discussed on the previous page. The elapsed time just happens to be the time at which this screen was captured. The total elapsed time is not seen because as soon as the carriage reaches the opposite end, there is a short time delay of a few tenths of a second while the data are calculated and written to the disk, then the motor is reversed and the carriage goes in the opposite direction.

Figure 17-12, This is the first of six data collections tests for determining the equation of the relationship between voltage from the analog-to-digital converter to carriage speed in centimeters per second. Note the “-” sign for the analog-to-digital polarity.

When the first run has ended, we obtain a new display, see Figure 17-13, below. Note that the voltage sign is now positive and its value is "6.00" volts.

Figure 17-13, This screen shows that we have increased the voltage from the analog-to-digital converter by 1.0 volts and that the polarity sign is now “+.”

The second run has now ended and we obtain a new display, see Figure 17-14, below. Note that the voltage sign is now negative and its value is "7.00" volts.

Figure 17-14, This third screen in the series shows that we have increased the voltage from the analog-to-digital converter by 1.0 volts and that the polarity sign has now returned to “-.”

The third run has now ended and we obtain a new display, see Figure 17-15, below. Note that the voltage sign is now positive and its value is "8.00" volts.

Figure 17-15, This fourth screen in the series shows that we have increased the voltage from the analog-to-digital converter by 1.0 volts and that the polarity sign is now “-.” The polarity will switch back and forth from positive to negative as the bed goes to the right and then to the left.

The fourth run has now ended and we obtain a new display, see Figure 17-16, below. Note that the voltage sign is now negative and its value is "9.00" volts.

Figure 17-16, We are now only one run from the end of this series. Note the “-” polarity again.

The fifth run has now ended and we obtain a new display, see Figure 17-17, below. Note that the voltage sign is now positive and its value is "10.00" volts. This is the last run in our demonstration series.

Figure 17-17, This is the last run in the series.

Figure 17-18, below, shows the new speed coefficients that have been obtained from our demonstration. Note the excellent correlation coefficient, 0.99994, that says that we have a "perfect fit" of the data to the line.

Figure 17-18, The six runs have finished and the computer has calculated the results.

Figure 17-19 shows a graph of the calibration data. Note that the data points are essentially directly on the line, as we would expect from the excellent correlation coeffiecient that was obtained.

Figure 17-19, This shows the graphical results of the speed calibration. Note that we have a very good fit with a correlation coefficient of 0.99994.

We want to save these data because they are the most recent speed calibration, so respond "Y" to the question.

Figure 17-20, Do we want to save the data? Yes, because this is a new calibration.

To save the data we may enter the correct password as shown in Figure 17-21, below.

Figure 17-19, Enter your password.

Table 17-3, below, shows the final output of our demonstration linear speed calibration.

Table 17-3 This is the final output from the linear speed calibration.
93/02/18
Rpm Intercept	:    0.0
Rpm Slope	:    0.0
RPM D/A Range	:    0
Linear Intercept	:    -0.023401179
Linear Slope	:    0.077463045
Linear D/A Range	:    4
Linear Distance	:    195.2

17.2.2.2. Manual Operation

As we have stated earlier, the advantage of manual operation lies in the fact that you can allow the device to move a relatively short distance for some or all of the runs. The advantage of this is the savings of time. The disadvantage is that the accuracy and precision of the final results are not nearly as good as the automatic operation. We recommend automatic operation whenever possible.

If you elect to do a manual calibration, then when you see the question

• Run speed calibration fully automatically (Y/N) ?

answer “N.”. You will be asked the same types of questions regarding the DAC02 (see Figure 17-11). Now for each voltage you may press the limit switch whenever you wish, stopping the carriage. You must measure the distance the carriage has traveled and enter this value when the computer asks:

• Full length bed travel (in.) 72.25

Let us assume that the carriage traveled only 23.625 inches. Type this number so the line would read:

• Full length bed travel (in.) 23.625

You will have to do this for each voltage. However, once the voltage from the analog-to-voltage converter has reached higher numbers, you may enter the actual length of the total bed travel and just press the <ENTERƒ> key for each remaining entry.

At the completion of all voltages the calculations are done just as in the fully automatic method.

17.3. Rotational Speed Calibrations

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We will now perform the same type of calibration for the rotational speed of a waste analyzer. As was stated on Page 17-4, the same mathematics applies to the calculation of the rotational speed of the Waste Analyzers. The major difference is that we are working in revolutions per second. Since the turntable always makes one revolution, we shall calculate revolutions per second.

The speed of the turntable is controlled by the computer. A current ranging from 4 to 20 milliamperes is sent from a digital-to-analog converter to the motor speed controller which then converts this to a 0 - 90 volt direct current signal which powers the motor. For example, a motor voltage of 90 volts will rotate the turntable one revolution in slightly less than 1 minutes, while a motor voltage of 10 volts will make the turntable move one revolution in about 45 minutes. Don’t confuse motor voltage with DAC voltage.

Figure 17-22, This is the opening screen of the Linear Speed Calibration Program.

For this calibration we used currents from the digital-to-analog converter ranging from 7.0 to 20.0 milliamperes. The incremental change in the current was set to 0.5 milliamperes per step. See Figure 17-23, below.

Figure 17-23, We are now going to perform a rotational speed calibration using currents from the analog-to-digital converter ranging from 7.0 mA to 20.0 mA.

The resulting graph is shown in Figure 17-24, below.

Figure 17-24, This is the graphical presentation of the rotational speed calibration.

Table 17-4, below, shows the final results of the rotational calibtration.

Table 17-4, This is the output from the rotational speed calibration.
93/02/23
Rpm Intercept	:   -0.625958912954
Rpm Slope	:    0.100380733009
RPM D/A Range	:    7
Linear Intercept	:    0.0
Linear Slope	:    0.0
Linear D/A Range	:    0
Linear Distance	:    0.0

This is the end of Chapter 17, “Linear and Rotational Speed Calibration.”