The furnace profile should be regularly checked and adjusted (twice per year is recommended). The profile can be performed with the cell completely frozen or melted, and our prefer method in our labs is to keep it frozen during the profile test. Next are the steps to perform the profile:
1. Before performing the furnace profile make sure the calibration parameters have not been altered from its original values when the 9260 was calibrated at the factory if you are doing it for the first time. Please check the flow chart in the user’s guide page 28 to learn how to reach each of the parameters and make changes as needed.
2. Wearing free powder rubber gloves pour a little bit of ethanol on a lint free wipe to clean the sheath of the SPRT which is going to be used to perform this test before inserting it into the well. Then connect it to your reference readout, and make sure the SPRT’s coefficients are programmed in the readout.
3. Set the scan rate to a maximum of 2?/minute, and the temperature to 155°C for Indium, 225? for Tin, 415°C for Zinc or 665°C for Aluminum, and after the furnace reaches this temperature wait for about 45 minutes until the 9260 and SPRT become stable. You can also monitor on the readout if the SPRT is stable enough to start the test.
4. Proceed to have the readout ready to record data. If you are using the 1594A or 1595A insert the thumb drive to record data.
5. The temperature needs to be measured at 3 locations: t1 with the SPRT fully inserted, t2 with the SPRT withdrawn 2.5”, and t3 with the SPRT withdrawn 5”. To reduce the effects of temperature drift we recommend taking again t2 and t1 in descent order. For this reason, the measurements should be done in the following order: t1, t2, t3, t2, t1. Before you start taking the data change the Scan Rate to 4°C/min in the 9260. Next are the settings for the 1594A/1595A reference readout.
6. After the SPRT was sitting at the t1 position for 45 minutes, start recording data for 4 minutes with a sample period of two seconds. Then using a paper clip (or lab stand), place the SPRT at the t2 position and start taking data for 4 minutes. Now move the SPRT to the t3 location and start recording data again for 4 minutes. Lower the SPRT to the T2 position and then record data for 4 minutes. Finally repeat the same process for the t1 position.
7. Select the last 20 samples at each temperature and calculate the average. Then if t2-t1<0.1? & t3-t1<0.2 the furnace profile passes.
8. If after computing the temperatures we found that T3-T1 is larger than 0.2?, we recommend applying the following “rule of thumb” to make changes to the percentage of power of the heaters:
“On the Aluminum, Zinc, Tin, and Indium fixed-point cells for every 2% of change to the bottom or top heaters the temperature will change about 0.2°C”
9. For example: if T3-T1=0.25 ? and we want this difference to be less than 0.2°C, we need to perform a linear increase of the percentage of power to the bottom heater. For this example, we would like to have t3-t1=0.15?, and this means that we need to decrease 0.1 ? to get to 0.15 ? (0.25-0.15=0.1). By applying the rule of thumb, we calculate the percentage of power that we need to increase:
Bottom % of power to increase = (2%*0.1)/0.2 = 1%
For this example, 1% is the amount of power that we need to increase to the top heater in the 9260.
10. Now try a new iteration for t1, t2, t3, t2, t1 and calculate again t3-t1 & t2-t1. If for any reason t3-t1 & t2-t1 are not within specs, you need to repeat steps 8 and 9.