Lutron PWH-303 Measures Water Hardness, Conductivity and Temperature, Remote CDPB-04 Probe
The Lutron PWH-303 measures the conductivity of water and reports it either as conductivity in microsiemens or as hardness in parts per million, switched with one button. A built-in temperature sensor reads the water temperature on the second line of the display at the same time, and automatic temperature compensation corrects the reading so a sample at 50 °F and the same water at 90 °F give the same answer.
Hard water carries dissolved minerals — principally calcium and magnesium — that scale pipes, water heaters, boilers and coffee equipment, and that keep soap and detergent from doing their job. Knowing the number tells you whether water needs treatment, and whether the softener or filter you already have is still working.
The probe is on a separate cable rather than built into the body, so it reaches into a tank, a sump, a well casing or a narrow container while the display stays in your hand. The meter is rated IP67 — dust tight, and protected against temporary immersion.
NOTE: This meter measures electrical conductivity and converts it to a hardness figure. Conductivity responds to all dissolved ions, not to calcium and magnesium alone, so the ppm reading is an estimate of total hardness rather than a titration result. That is the right tool for tracking, comparing and screening water. Where a certified hardness number is required — a laboratory report, a regulatory filing — use a titration method.
Typical Applications
- Checking household water before and after a softener or filter, and confirming the softener is still regenerating.
- Well water testing and periodic monitoring.
- Reverse osmosis and deionized water systems — verifying product water purity and spotting a spent membrane or cartridge.
- Aquariums, ponds and fish hatcheries.
- Hydroponics, greenhouses and irrigation water.
- Swimming pools and spas.
- Boilers, cooling towers and humidifiers, where scale and carryover are the concern.
- Coffee, espresso and beverage production, where water chemistry drives both flavor and equipment life.
- Food processing, rinse water and clean-in-place verification.
- Photographic processing.
- Laboratory, quality control, schools and colleges.
Features
- Pen type meter with a separate corded electrode, for fast digital readings in places a one-piece pen will not reach.
- Conductivity (µS) or hardness (ppm) selected with one button.
- LCD with two lines, showing hardness or conductivity and the temperature value at the same time.
- User calibratable against a conductivity standard solution. Download the calibration instructions.
- Built-in temperature sensor with ATC, so readings are corrected for water temperature automatically.
- Temperature displayed in °F or °C, and the choice is remembered when the meter is switched off.
- Separate platinum glass electrode, high performance for pure water low conductivity measurement, and long service life.
- IP67 rated, dust tight and protected against temporary immersion.
- Data hold function freezes the displayed value.
- Records maximum and minimum values with recall.
- Auto power off after 10 minutes saves battery life.
- Microcomputer circuit for high accuracy.
- Compact and light, powered by four AAA batteries.
Specifications
- Conductivity range: 0 to 1999 µS (2000 µS range), 1 µS resolution, auto ranging.
- Hardness range: 0 to 1000 ppm, 1 ppm resolution, auto ranging.
- Conductivity and hardness accuracy: ± (3% F.S. + 1 digit) at 23 ± 5 °C.
- Temperature range: 32 to 140 °F (0 to 60 °C), 0.1 degree resolution.
- Temperature accuracy: ± 1.5 °F (± 0.8 °C).
- Temperature compensation: automatic from 32 to 140 °F (0 to 60 °C), with a compensation factor variable between 0 and 5.0% per degree Celsius.
- Electrode: platinum glass, for long life and low conductivity (pure water) measurement.
- Display: 20 x 28 mm dual line LCD.
- Display sampling time: approximately 0.8 second.
- Circuit: custom one-chip microprocessor LSI.
- Data hold: freezes the displayed reading.
- Memory recall: maximum and minimum values.
- Power off: manual by push button, or automatic after 10 minutes with no button pressed.
- Enclosure rating: IP67.
- Meter dimensions: 7.5 x 1.6 x 1.6" (190 x 40 x 40 mm).
- Weight: 6.0 oz (171 g).
- Operating temperature: 32 to 122 °F (0 to 50 °C). NOTE most batteries are not rated for use below -4 °F or above 125 °F.
- Operating humidity: less than 80% RH, non-condensing.
- Power supply: four 1.5V AAA (UM-4) alkaline batteries or equivalent.
- Power consumption: approximately 5.7 mA.
Water Hardness Reference
The classifications below are general guidance for interpreting a reading. They are not a standard; where a specific limit applies, use the figure your equipment manufacturer, code or client specifies.
| Conductivity (µS) |
Hardness (ppm) |
Classification |
| 0 to 140 |
0 to 70 |
Very soft |
| 140 to 300 |
70 to 150 |
Soft |
| 300 to 500 |
150 to 250 |
Slightly hard |
| 500 to 640 |
250 to 320 |
Moderately hard |
| 640 to 840 |
320 to 420 |
Hard |
| Above 840 |
Above 420 |
Very hard |
Specifications are tested in an environment with RF field strength less than 3 V/m and frequency less than 30 MHz.
Accessories Included
- Platinum glass conductivity probe, CDPB-04.
- Operation manual.
- Lutron factory calibration card.
Optional Components
- High sensitivity conductivity probe, CDPB-03.
- 1.413 mS conductivity calibration standard, CD-14.
- Soft carrying case, CA-52, 8.3 x 3.1 x 2.0" (210 x 80 x 50 mm).
- Hard carrying case, CA-06, 11.0 x 7.7 x 2.6" (280 x 195 x 65 mm).
