2020e/2020i Turbidity Meter Troubleshooting Guide

Negative Results

The 2020e and 2020i turbidity meters will display negative results if the sample water is less turbid than the blank reading. This is possible in ultralow turbidity waters, where the sample turbidity is at or near the detection limit of the meter.

Negative readings can also indicate a problem when the meter was blanked. If the meter is accidentally blanked to a 1.0NTU standard, subsequent tests may negative, in response to the high blank reading. Correct this problem as follows:

1. Reset the meter to the factory calibration settings: with the meter turned OFF, hold down the *OK button and press ON. Release both buttons at the same time. Press *OK to select the default settings. Press *OK again and the meter will turn off. The factory settings will be restored.
2. Follow the instructions on how to properly fill the turbidity tubes with the standard solutions (see below).
3. Once the tubes are filled with standard, turn the turbidity meter on and enter the measurement mode. Scan the blank tube (0.00 NTU). Then leave the blank tube in the meter and press *OK to scan the blank as a sample. It should read 0.00. If not, press the UP button and re-blank the meter again. Then scan the blank as a sample again until it reads 0.00. This may take at least three tries.

NOTE: a small negative number will be observed if the reading is slightly less than the reading used as a blank. This is expected due to minute variations between readings. A reading of -0.02 or even -0.04NTU is not uncommon. Once 0.00 or a very small negative number is achieved, the meter is ready to be calibrated.

Filling Turbidity Tubes

It is important to use the proper test tube designed for use with the 2020e and 2020i turbidity meters, LaMotte code 0475. Tubes must be clean and free from fingerprints, lint, dried spills and significant scratches. Use lint free tissue to wipe your tubes clean.

When filling a tube with standard solution, rinse the vial with a small amount of the standard solution, three times, then fill to the line. This will assure that no dust, debris or dirt will contaminate the standard solution that you pour into the vial. Put a dry tube positioning ring on the tube. The tube positioning ring has two tapered notches and one squared-off notch. Place the ring on the tube so that the one squared-off notch is aligned with the vertical, white indexing line that extends 90° from the horizontal fill line on the tube. This will assure that you properly index the tube inside the light chamber each time. Wipe any liquid that may have leaked between the positioning ring and tube surface. Cap the tube and apply an Avery label marked with the corresponding NTU value.

Unstable Readings

Unstable readings can occur when excessive physical change occurs in the sample at the time that the sample is scanned in the meter. Settling and sedimentation can cause this in high turbidity waters and even microscopic air bubbles and submicron particulates can cause this in low turbidity waters. The ERR4 “Processing Error” may be triggered in response to these situations.

To obtain the most accurate and stable readings possible, utilize the signal averaging feature of the meter. Turn the meter on and select Options, then Averaging. Choose between 2, 5 or 10 measurements. Press OK, then press the back button to return to the main menu. Signal averaging of 5 measurements is usually sufficient and provides optimal balance of the signal averaging benefits, with minimal stress to the battery.

Power Problems

Be sure to use brand name 9V alkaline batteries. Heavy Duty, Rayovac and store brand batteries do not have enough sustained power to keep the meter on and power the lamp. We suggest Duracell Alkaline 9V batteries. Rechargeable batteries can be used; we suggest Duracell or Energizer 9V NiMH rechargeable batteries. If using the meter in a lab setting, remove the battery altogether and operate exclusively with the appropriate type of AC Adapter designed for the 2020e and 2020i meters. LaMotte offers the AC adapter as an optional accessory, code number 1754.

If there is any visible damage to the battery connector, contact LaMotte Technical Services for a Return Authorization Number and to make arrangements to have your meter repaired. Any un-authorized alterations to the meter will void the warranty.

Calibration

See pages 32 and 33 for calibration instructions. The 2020e and 2020i are capable of one point calibrations. For greatest accuracy, blank the meter first, using an appropriate 0.00NTU blank standard. The blank reading does not count as a calibration point. It is a reference standard for improved low level detection and calibration. After blanking the meter, select one standard solution to calibrate the meter to. This can be a 1.0, 10, 100 or other formazin solution. Remember, the meter is only capable of a one point calibration. Calibrate to 1.0NTU if samples are expected to be 1.0NTU or less. Calibrate to 10.0NTU if samples are expected to be greater than 1.0NTU.

Err 1 Message

Low Battery. See “Power Problems” above.

Err 2 Message

An attempt was made to calibrate the meter outside of the allowable range. The 2020 meters will not allow the user to recalibrate when the initial reading of the standard solution deviates greater than 50% of the standard concentration. A reading of 0.49NTU is too low for a 1.0NTU standard and calibration up to 1.0NTU will not be possible. This may occur if the standard solutions are out of specification or if there was a problem blanking the meter prior to calibration.

Check to make sure that the standard solution is appropriate for use with the 2020e or 2020i. LaMotte Company makes the standard solutions specifically for the 2020e and different standards that are specific for the 2020i. Turbidity standard solutions cannot be interchanged. Confirm by matching the code numbers on the bottles to the 2020 manual. Formazin standards may be used, if prepared accurately and used while fresh.

If the standards are within their shelf life, try resetting the meter to factory calibration. See “Negative Results” above, or page 22 of the 2020 instruction manual for instructions on how to reset your meter to factory calibration.

Err 3 Message

An attempt was made to calibrate the meter with a zero sample. Only use the blank 0.00NTU standard to set a blank reading, then calibrate to LaMotte standard solutions.

Err 4 Message

Processing Error. See “Unstable Readings” above.

Err 5 Message

No blank reading. The meter has never been blanked. Must blank meter using 0.00NTU blank standard solution.

Err 6 Message

The meter must be re-blanked and the sample rescanned.

Err 7 Message

Call LaMotte Technical Service at 1-800-344-3100.

Repairs

If it is necessary to return the instrument for repair, telephone LaMotte Company at 1-800-344-3100 or fax 1-410-778-6394 for a return authorization number.