5
About Your HHWT-11 Instrument
In order to save power, the meter is designed to turn off after 3 minutes (timed from the last button pressed).
Should the meter turn off in the middle of a test, the last stored zero in the meter will remain valid when the
meter is turned on again. Also, the test result is stored in memory for easy retrieval.
The HHWT-11 meter is controlled by three buttons:
1. ZERO/ON:KHQ¿UVWSUHVVHGWKLVEXWWRQWXUQVWKHPHWHURQ:KHQWKHPHWHULVRQDQGWKLVEXWWRQLV
pressed, it zeroes the sample in the cell. Once the meter is zeroed, this zero value applies to all parameters
and is stored and retained even when meter turns off. However, it is recommended that each new water
sample analyzed is zeroed before testing, to maximize sensitivity and accuracy.
2. MENU: With each press, the MENU button advances through the tests in the following sequence: CL1,
bR2, O3, Cd4, PA5, HP6, PH7, HR8. Each test menu can store up to 20 results. To retrieve the stored
results, go to the desired test using the MENU key. When the desired test is displayed, press and hold
down the MENU key. Continue holding down the MENU key to scroll the stored results for that test, starting
with the most recent result. The meter will display, from memory, the last 20 readings in sequence beginning
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the oldest result retained. Only the last 20 readings are stored in each menu. This meter is able to store 160
results in memory (20 in each menu).
3. READ: When pressed once, this button starts the timer for the parameter being tested. When pressed a
second time the meter exits the timer and immediately prepares to colorimetrically measure the sample, and
simultaneously stores the measurement in memory.
If the parameter being measured is below or above the detection range, the display will show “LO” (Under
Range) or “HI”2YHU5DQJHUHVSHFWLYHO\7KLVIHDWXUHLVPHQXVSHFL¿FDQGGRHVQRWDSSO\WRDOOSDUDPHWHUV
AWWA
4500-Cl G Strip
DPD-1
Anhydrous DPD sulfate
Anhydrous Na2HPO4
Anhydrous KH2PO4Na2
EDTA
1.5%
33.4%
64.0%
1.1%
1.5%
33.4%
64.0%
1.1%
Component
(Free Chlorine)
About The Accuracy / Calibration Of The Chlorine Plus System
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spectrophotometric methods. The algorithm in the software of the HHWT-11 Systems mirrors the
AWWA, US EPA , DIN, and ISO reference test methods for chlorine. Studies show that the HHWT-11
System, with the HHWT-486637 (DPD-1), repeatedly agrees with an EPA Compliant reference method
greater than 99% (R2= 0.9989, 0 - 6.0 ppm - see page 14). The HHWT-11 Advanced Photometric
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meter to be valid for the life of the meter because of the quality, Long-Life LED, the photo cell, and the
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Reference Standard (part #HHWT-486602) is available for purchase (see page 13).
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This DPD test system is accepted by most health departments because this test is USEPA (DIN
Standard 38 408 G4, ISO 7393/2) accepted for testing requirements for Free and Total Chlorine. The
Chlorine Plus meter uses a wavelength of 525nm; and the compliance requirement is that the
colorimeter wavelength is between 490 and 530nm. The HHWT-486637 (DPD-1) uses the same
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by AWWA (American Water Works Association) method 4500-Cl G. It should be understood that the
USEPA does not "approve" commercial DPD delivery systems such as reagent powder pillows, tablets,
dispensers, or Strip DPD delivery devices. The HHWT-486637 (DPD-1) for Free Chlorine, and the
HHWT-486638 (DPD-3) or the HHWT-486670 (DPD-4) for Total Chlorine meet your reportable testing
requirements because the HHWT Strips deliver the same chemicals in identical proportions (see table
below); therefore, the system is compliant. Likewise, AWWA proportions are followed as required for
Total Chlorine measurements using Potassium Iodide.
