Direct Soil Measurement pH Meter - HI99121

In stock
The HI99121 is the perfect portable  Direct Soil Measurement pH Meter. With the HI99121 and HI1292D direct soil pre-amplified pH and temperature probe, users can test both the pH of soil directly or after preparation of a soil slurry with deionized water. The HI1292D features a conical, rugged tip that can be directly inserted into moist or soft soil. For harder soils, the kit includes a plastic auger to perforate the ground.

• Simultaneous pH and temperature measurements on a large dual-line LCD display

• User-friendly two button design

• Application specific probe

• Durable IP67 waterproof casing

• Watertight probe connection

• Probe condition indicator

• Automatic pH calibration at one or two points within two memorized buffer sets (standard or NIST)

• On-screen calibration tags

• mV of pH measurement for electrode check

• Selectable temperature unit (°C or °F)

• Auto-off function

• Battery life indication and low battery detection

• Soil preparation solution


Soil can be acid, neutral or alkaline, according to its pH value. Most plants prefer a pH range from 5.5 to 7.5; but some species prefer more acid or alkaline soils. Nevertheless, every plant requires a particular range of pH, for optimum growth. pH strongly influences the availability of nutrients and the presence of microorganisms and plants in the soil. For example, fungi prefer acidic conditions whereas most bacteria, especially those supplying nutrients to the plants, have a preference for moderately acidic or slightly alkaline soils. In fact, in strongly acidic conditions, nitrogen fixing and the mineralization of vegetable residual is reduced. Plants absorb the nutrients dissolved in the soil water and the nutrient solubility depends largely on the pH value. Hence, theavailability of elements is different at different pH levels. Each plant needs elements in different quantities and this is the reason why each plant requires a particular range of pH to optimize its growth. For example, iron, copper and manganese are not soluble in an alkaline environment. This means that plants needing these elements should theoretically be in an acidic type of soil. Nitrogen, phosphorus, potassium and sulfur, on the other hand, are readily available in a pH range close to neutrality. Furthermore, abnormal pH values, increase the concentration of toxic elements for plants. For example, in acid conditions, there can be an excess of aluminum ions in such quantities that the plant cannot tolerate. Negative effects on chemical and physical structure are also present when pH values are too far from neutral conditions (break up of aggregates, a less permeable and more compact soil).  The HI99121 meter features a large multi level LCD screen which displays both pH and temperature readings simultaneously with 0.01 pH resolution and an accuracy of ±0.05 pH. The LCD screen also has indicators for calibration status and stability, as well as on-screen tutorial messages. The HI99121 has many advanced features that are found in more expensive portable instrumentation including automatic calibration, buffer recognition,and temperature compensation. The battery percent level is displayed at start up alerting the user to the remaining battery power that is available. The supplied HI1292D is a glass body, amplified pH electrode with a built-in temperature sensor designed specifically for measuring the pH in soils.



pH Range 

-2.00 to 16.00 pH / -2.0 to 16.0 

pH Resolution 

0.01 pH / 0.1 

pH Accuracy 

(@25°C/77°F) ±0.02 pH / ±0.1 

pH Calibration 


Automatic, one or two-point selectable bufferset standard: 4.01; 7.01; 10.01 or NIST: 4.01; 6.86; 9.18 

pH-mV Range 


mV Resolution 


mV Accuracy (@25°C/77°F) 


mV Temperature Range 

-5.0 to 105.0°C; 23.0 to 221.0°F 


0.1°C; 0.1°F 

Accuracy (@25°C/77°F) 


±0.5°C (up to 60°C), ±1.0°C (outside); ±1.0°F (up to 140°F), ±2.0°F (outside) 

Additional Specification 


Temperature Compensation 

automatic, from -5.0 to 105.0°C (23.0 to 221.0°F) 



(included) HI12923 glass body, pre-amplified pH electrode for soil measurement with internal temperature sensor, DIN connector and 1 m (3.3’) cable 

Battery Type 

1.5V AAA (3) approx. 1400 hours of continuous use 

Auto off 

user selectable: after 8 min, 60 min or disabled 


0 to 50°C (32 to 122°F); RH max. 100% 



154 x 63 x 30 mm (6.1 x 2.5 x 1.2”) Meter Mass (with batteries) 196 g (6.91 oz.) 

Case Ingress Protection 

Rating IP67 

Ordering information 


HI99121 is supplied with HI12923 pH/temperature probe with glass body and Quick Connect DIN connector with 1m (3.3’) cable, pH 4.01 and 7.01 Buffer sachets, HI700663 electrode cleaning solution sachet for soil deposits, HI700664 electrode cleaning solution sachet for humus deposits, HI7051M soil preparation solution, HI721319 ground auger, 100 mL beaker, 1.5V AAA batteries (3), calibration certificate of meter, calibration certificate of probe, instruction manual and HI710142 rugged carrying case.