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sensor or a process upset) from keeping a control relay switched on
continuously. The overfeed timer setting limits how long the relay and its
connected control element stay on independent of the conditions.
When a relay overfeed timer is used and it has expired, the relay status
flashes on the Measure screen until the overfeed timer is reset. Push
Menu and select TEST/MAINT>OVERFEED RESET to reset the
overfeed timer.
Reset the configuration
To set the configuration to the factory defaults:
1. From the Measure screen, push MENU and select
TEST/MAINT>RESET CONFIG.
2. Push ENTER to confirm.
Note: Push ESC to not set the configuration to the factory defaults.
Calibration
Primary calibration and sample calibration
Before initial use and every 3 months, do a primary calibration or sample
calibration to meet USEPA regulations. Regardless of the type of
calibration used, the steps are the same. The only difference is the
solution used.
• Primary calibration—20 NTU or 40 NTU primary standard (formazin
suspension or StablCal)
Note: The USEPA requires 40 NTU primary standard to comply with Method 2.
• Sample calibration—A sample with a known turbidity value
*
For the best results, prepare formazin solution with Class A laboratory glassware.
Prepare 4000 NTU formazin suspension (primary calibration only)
W A R N I N G
Chemical exposure hazard. Obey laboratory safety procedures and
wear all of the personal protective equipment appropriate to the
chemicals that are handled. Refer to the current safety data sheets
(MSDS/SDS) for safety protocols.
Items to collect:
• Distilled water
*
• Volumetric flask (4x)
• Reagent-grade hydrazine sulfate, (NH
• Reagent-grade hexamethylenetetramine, (CH
1. Pour some distilled water through a 0.2 micron filter into each flask.
Rinse each flasks at least two times with the filtered water
2. Fill one flask with at least 1000 mL of the filtered water.
3. Solution 1: In a second flask, dissolve 5.00 grams of reagent-grade
hydrazine sulfate in filtered water. Dilute the solution to 500 mL with
filtered water. Gently swirl to mix.
4. Solution 2: In a third flask, dissolve 50.00 grams of reagent-grade
hexamethylenetetramine in filtered water. Dilute the solution to
500 mL with filtered water. Gently swirl to mix.
5. In a fourth flask, mix 50.0 mL of Solution 1 and 50.0 mL of Solution
2 to make a 4000 NTU stock turbidity suspension. Gently swirl to
mix.
6. Let the mixture stabilize for 24 hours at 25 °C, ±3 °C (77 °F, ±5.4 °F).
7. Pour the stock suspension into an amber glass (or other UV-light
blocking) bottle for storage. When kept at room temperature and in
)
H
SO
, 5 grams
2
2
2
4
)
N
, 50 grams
2
6
4
English 21
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