HM Digital PH-200 Waterproof pH and Temperature Meter
by Hydrofarm
 |
List Price: Our Price: $79.08 You Save: $65.91 (45%) Availability: Usually ships in 1-2 business days Buy Used: from $59.99 (click here) Category: Lawn & Patio See more product details |
Product Details
Manufacturer: HydrofarmBrand: HM Digital
Edition: Lawn & Patio
Model: HMDPH200
Publisher: Hydrofarm
Studio: Hydrofarm
Music Label: Hydrofarm
Product features:
- Measures pH and temperature
- Auto ranging 3 point calibration with digital fine tuning
- Simultaneous temperature display
- Measurement range 0-14 pH
Tools and Hardware Reviews of HM Digital PH-200 Waterproof pH and Temperature Meter
Customer Review: Notes on using the PH-200
Summary: 3 Stars
HM Digital Meters Waterproof pH/Temperature Meter
I received the pH meter with a dry head - the buffer solution in the cap fully evaporated; the instrument settles measurements not in the specified 30 seconds, but more like in 3 minutes (I fully clean and dry the reference and measurement probes on the tip of the instrument before each use).
There are indeed some O-rings that are supposed to prevent moisture from getting into the battery compartment or inside the measurements tip when maneuvering the instrument. However, one has to definitely avoid stream washing the tip while holding the instrument upwards: this will let moisture get inside the tip and create significant measurement errors (I would not call this device waterproof; since it cannot withstand a stream of water in the probes area it would not truly qualify even for the IP66 standard). Before each measurement, one needs to clean and dry the pH reference and pH measurement probes and insure that the display is showing dashes, not numbers, in the pH area.
I also found that calibrating with a standard reference solution of pH 4.01 generates significant better results - at least for the acidic pH range, than after calibrating with the pH 7.0 reference solution. I used "General Hydroponics" standard solutions:
1)If the instrument is calibrated on pH 7.0 reference solution, then it will read the pH 4.0 reference solution as being of pH 3.92 (I did this calibration several times - cleaned and dried heads each time, the stable readings - after 3 minutes, were consistent)
2)If the instrument is calibrated on pH 4.01 reference solution, then it will read the pH 7.0 reference solution as having a pH of 6.99 (again, ran several calibrations with consistent final readings)
The above results in (1) may look a bit surprising, however - if considered normal, then one could conclude that a calibration with a pH 7.0 reference solution would also yield more precise readings for basic solutions (this needs to be verified though)
The dual pH/Temperature display makes comparison measurements meaningful, particularly for temperatures less than 25degC or larger than 45degC, where there is an increased dependency of pH measurement with liquid temperature. A temperature compensation of the pH measurement seems to be implemented, but is more effective in the 25-45degC range. For a liquid with (pH7.29 at 1.5degC), the pH dropped to (7.12 at 15degC) to (7.05 at 25degC), hit a bottom (pH7.02/7.03 between 35-45degC) then started to rise after 45degC to read (7.08 at 52.5degC) where I stopped.
As far as other functional features, the one that I would have liked to be different is the automatic shut down timing, which should be programmable to allow for observation of longer processes. The default (and only) time-out value proved to be short for what I needed to do so far, and whenever one changes the position of the instrument in the liquid (to turn the meter back on), a temporary instability in the pH reading occurs.
The assembly is sturdy enough for daily usage and I did not have major issues handling it or pressing its buttons. I have been using the instrument almost each day for a month now.
Description of HM Digital PH-200 Waterproof pH and Temperature Meter
Hydrofarm hmdph200 waterproof ph and temperature meterAccessories Tools
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