Hach AS950 Fonctionnement page 19

5. For the refrigerated sampler, put a graduated cylinder under the distributor outlet or composite
tube support in the refrigerated cabinet.
6. For the portable sampler, put the tubing from the outlet side of the pump into a graduated
cylinder.
7. Push CALIBRATION, then select Volume>Sample Volume.
8. Push Next.
9. Enter the volume of sample to collect.
10. Push Grab. The pump operates in reverse to purge the intake tube. The pump then operates in
the forward direction and collects the sample volume. The pump operates in reverse to purge the
intake tube.
11. After the sample is collected, compare the volume of the sample in the graduated cylinder with
the sample volume entered.
12. If the collected volume is different from the entered sample volume, enter the volume that was
actually collected. Push Next. The controller is adjusted to accurately measure all programmed
volumes.
13. To verify the calibration, push Verify.
14. To save the calibration, push Finish.
4.2.1.2 Adjust the sample volume calibration (optional)
For the best sample volume accuracy, adjust the sample volume calibration. When the sample
volume is less than 200 mL, the manufacturer recommends that the sample volume calibration is
adjusted.
1. Select Hardware Setup>Liquid Detect>Status. Make sure that the liquid detector is enabled.
2. For the refrigerated sampler or AWRS sampler, collect three grab samples of the volume that is
specified in the sampling program. Refer to the expanded user manual on the manufacturer's
website.
Note: As an alternative, collect three samples with the sampling program. Refer to step 3.
3. For the portable sampler, collect three samples in one bottle (or three bottles) with the sampling
program. For the best accuracy, collect three samples in one bottle. If necessary, change the
sampling program to immediately collect the samples.
Note: Do not use grab samples to adjust the sample volume calibration of a portable sampler.
4. Pour the three samples into a graduated cylinder to measure the total sample volume.
5. Divide the total sample volume by 3 to get the average sample volume.
6. Calculate the adjustment value:
(target sample volume – average sample volume) ÷ target sample volume × 100 = adjustment
value
Where:
Target sample volume = the volume that is specified in the sampling program.
For example, if 200 mL is the target sample volume and the average sample volume is 202 mL,
the adjustment value is –1%.
7. Push MENU.
8. Push CALIBRATION, then select Volume>User Adjust.
9. Enter the adjustment value (e.g., –1%), then click OK.
10. For the refrigerated sampler or AWRS sampler, collect another grab sample as follows:
a. Push Verify.
b. Enter the sample volume that is specified in the sampling program.
c. Push Grab.
Note: As an alternative, do steps 3–5 again.
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