Table of Contents
UHSAS Calibration
- Need to be logged in under the Configuration tab in order to perform the calibration.
Zero Count Test
- Hook up a filter to the inlet of the UHSAS.
- Hook up an external pump to the exhaust side of the UHSAS.
- Turn on the pump and UHSAS.
- Allow the UHSAS to run for several minutes; watch the instrument output to see that the UHSAS is counting zero particles.
- If the UHSAS is counting particles, check for leaks in the filter-UHSAS-pump system.
- If the UHSAS is still counting particles and there is no leak, consult the operator's manual.
Initial Ambient Air Calibration
- This calibration sets up the calibration curve that the UHSAS uses to size measured particles.
- This calibration should be done on a non-precipitating day and outside or at least in a hanger with the door open.
- Turn on the UHSAS and make sure that the pump is running (or hook up an external pump).
- Click on the Calibration tab. It will show a display similar to the picture below.
- Click on the G3:G2 Gain tab.
- Click on the Clear, then the Run button to measure the G3:G2 gain parameters. Then click Save to save the new measurements to the calibration curve.
- Repeat step 4 for both the G2:G1 Gain and the G1:G0 Gain measurements.
Nebulizer Point Calibration
- This is to create anchor points to help the calibration curve size measured particles more accurately.
- There are four gain stages for the UHSAS. The gain stages are the regions between the red dots on the calibration curve above. The region to the left of the left red dot is the Gain Stage 3 region, the region between the left and the middle red dots is the Gain Stage 2 region, the region between the middle and the right dots is the Gain Stage 1 region, and everything to the right of the right dot is the Gain Stage 0 region.
- Try to pick particle sizes that do not fall near (within 20 nm or so) of the stitch points for best results.
- Hook up Nebulizer to UHSAS inlet.
- Put in selected size of particles into the Nebulizer.
- Go to the Map Tab for the UHSAS, click the button corresponding gain stage (look at current calibration curve to find out which gain stage the current particle size falls under), click the voltage button, input the desired voltage range, click the linear button, and finally the commit button.
- Click the Histogram tab at the top, then click Run to see the histogram.
- Change the integration time to a time between 10 and 30 seconds.
- Find the voltage that contains the maximum number of counts (peak voltage).
- Once the peak voltage has been found, click the Calibration tab, either click on the up arrow on the top left corner of the screen to find the point that is the same size of particle that is currently being sized, or click the up arrow until the the first unused point is reached.
- Select the gain stage, enter in the particle size and the peak voltage (doesn't have to be exact) and click Commit. The edited point should move to the new voltage value given (or a new point will appear if a new point was used).
- Click the Map tab, Click the Size button, enter the size range that will accommodate the current size of particles, click either Linear or Log, then click Commit.
- Click on the Histogram tab, and click Run. Find the peak size that the UHSAS is counting and see if that size bin includes the actual size of the current particles.
- If the particles are not being sized correctly, click on the Calibration tab and adjust the voltage of the current size point. Jumps of 50 millivolts work well. Adjusting the voltage up will make the UHSAS size the particle smaller and vice versa.
- Repeat steps 10 and 11 until the particle is being sized correctly. The displayed range of particles may need to be decreased around the actual size of the particle for more fine-tune adjustments of particle size.
- Remove current particles and put in the next size of particles, either washing out the jar or using a different jar to avoid contamination issues.
- Repeat steps 3 through 12 for each size of calibration particles. Running a calibration with one size per gain stage and with two sizes in the Gain 0 region is recommended.
- When done calibrating, remove all old points not used or adjusted in the current calibration.
- Change the integration time back to 1.0 seconds. Do this before the calibration is saved.
- Put several different size particles into the Nebulizer, one at a time, to test how good the calibration is.
- If the calibration looks good, click the Configuration tab and save the current calibration there. An older calibration can also be loaded into the UHSAS from this spot as well.