Sato SK-650PH Desktop Digital pH Meter

The Sato SK-650PH is a desktop digital pH meter for laboratory, industrial and general liquid measurement.

The meter displays pH together with temperature and provides functions for sensor-condition checking, calibration, data storage and computer connection. A sensor arm is supplied for positioning the electrode during measurement and for use together with a laboratory stirrer.

The SK-650PH is supplied without a pH probe. Select the probe according to the sample, measuring range and required electrode construction.

Key Functions

  • pH, temperature and mV display
  • Sensor sensitivity indication for checking electrode condition
  • Stability indication when the measured value has settled
  • Automatic temperature compensation with compatible probes
  • Date and time display together with measurement
  • One-, two- or three-point pH calibration
  • 99-reading data memory
  • RS-232C data output
  • Sensor arm supplied as standard
  • Multiple pH probe options for different applications

Calibration Points

The SK-650PH supports calibration using up to three points selected from the following standard solutions at 25°C.

Calibration PointStandard Solution
pH 4.01 Phthalate standard solution
pH 6.86 Neutral phosphate standard solution
pH 9.18 Borate standard solution
pH 10.01 Carbonate standard solution

SK-650PH Specifications

SpecificationDetails
Cat. No. 6427-00
Model SK-650PH
pH Display Range 0.00 to 14.00 pH
Temperature Display Range -6.0°C to 82.0°C
mV Display Range -2002 to +2002 mV
pH Resolution 0.01 pH
Temperature Resolution 0.1°C
mV Resolution 0.1 mV from -199.9 to +199.9 mV; 1 mV outside this range
pH Repeatability ±(0.01 + 1 digit) pH
Temperature Repeatability ±(0.1 + 1 digit)°C
Sampling Time Approx. 1 second
Data Memory Up to 99 readings
Output RS-232C
Operating Environment 5°C to 40°C, below 95%RH, non-condensing
Storage Environment -10°C to 50°C, non-condensing
Power Dedicated 9 VDC AC adapter
Material ABS resin body and sensor arm
Dimensions 215 (W) × 58 (H) × 170 (D) mm, excluding sensor arm
Weight Approx. 915 g, excluding sensor arm
Standard Accessories Sensor arm, AC adapter and instruction manual

Probe Selection

The measuring range and accuracy of the complete SK-650PH system depend on the probe connected to the meter.

Sato provides a standard PHP-31 probe together with the 640S Series for general-purpose, immersion, high-alkali, flat-surface, test-tube and small-sample applications.

PHP-31 Standard Probe

The PHP-31 is the standard combination pH and temperature probe for general liquid measurements.

SpecificationpHTemperature
Cat. No. 6400-30
Model PHP-31
Measuring Range 0.00 to 14.00 pH 0.0°C to 50.0°C
Accuracy ±0.28 pH from pH 0 to 2
±0.08 pH from pH 2 to 12
±0.38 pH from pH 12 to 14
±0.3°C from 20°C to 30°C
±0.5°C outside this range
Sensor Lead-free glass electrode Thermistor
Internal Solution Non-refillable KCl solution
Probe Size Ø12 × 135 mm
Cable Approx. 1 m
Weight Approx. 76 g

640S Series Optional pH Probes

Select the 640S probe according to the physical form and chemical condition of the sample.

Cat. No.ModelApplicationpH RangeTemperature
6424-00 640S-1 General purpose 2.00 to 13.00 0 to 50°C
6425-00 640S-2 Immersion / waterproof 2.00 to 13.00 0 to 50°C
6425-10 640S-3 High-alkali measurement 2.00 to 14.00 0 to 50°C
6425-20 640S-4 Flat-surface measurement 2.00 to 13.00 No built-in temperature sensor
6425-30 640S-5 Test tubes 2.00 to 13.00 No built-in temperature sensor
6425-40 640S-6 Minute / very small samples 2.00 to 13.00 No built-in temperature sensor

640S-1 General-Purpose Probe

The 640S-1 is intended for general liquid pH measurement. It contains both a pH electrode and temperature sensor, allowing automatic temperature compensation when connected to the SK-650PH.

pH Range 2.00 to 13.00
Temperature Range 0 to 50°C
pH Accuracy ±0.03 pH
Temperature Accuracy ±0.5°C
Liquid Junction Sleeve type
Internal Solution 3.3 mol/L KCl, refillable
Probe Size Ø12 × 156 mm
Cable 1 m standard; optional longer lengths available

640S-2 Immersion Probe

The 640S-2 has a waterproof probe construction and can be immersed in tanks or other suitable liquid samples.

pH Range 2.00 to 13.00
Temperature Range 0 to 50°C
pH Accuracy ±0.03 pH
Temperature Accuracy ±0.5°C
Liquid Junction Ceramic type
Internal Solution 3.3 mol/L KCl, non-refillable
Probe Size Approx. Ø34 × 147 mm
Cable 3 m standard; optional longer lengths available

640S-3 High-Alkali Probe

The 640S-3 extends the pH range to 14.00 and is intended for suitable high-alkali liquid measurements.

pH Range 2.00 to 14.00
Temperature Range 0 to 50°C
pH Accuracy ±0.03 pH
Temperature Accuracy ±0.5°C
Liquid Junction Sleeve type
Internal Solution 3.3 mol/L KCl, refillable
Probe Size Ø12 × 159 mm

640S-4 Flat-Surface Probe

The 640S-4 is designed for pH measurement of suitable flat surfaces such as leaves, skins and cut fruit surfaces.

pH Range 2.00 to 13.00
pH Accuracy ±0.03 pH
Operating Temperature 15 to 50°C
Temperature Compensation No built-in temperature sensor
Liquid Junction Sleeve type
Internal Solution 3.3 mol/L KCl, refillable

640S-5 Test-Tube Probe

The 640S-5 has a slender measuring section for insertion into test tubes and other narrow sample containers.

pH Range 2.00 to 13.00
pH Accuracy ±0.03 pH
Operating Temperature 10 to 50°C
Temperature Compensation No built-in temperature sensor
Measuring Section Ø6 × 190 mm
Overall Probe Length Approx. 270 mm

640S-6 Minute-Amount Probe

The 640S-6 is designed for very small samples such as a small droplet where a conventional pH electrode is too large.

pH Range 2.00 to 13.00
pH Accuracy ±0.03 pH
Operating Temperature 10 to 50°C
Temperature Compensation No built-in temperature sensor
Measuring Section Ø3 × 50 mm
Overall Probe Length Approx. 148 mm

Probe Selection by Application

Measurement RequirementProbe
Standard general liquid measurement PHP-31 or 640S-1
Probe immersed into a tank 640S-2
Higher-alkalinity samples 640S-3
Flat or cut surface 640S-4
Narrow test tube 640S-5
Very small sample volume 640S-6

Automatic Temperature Compensation

Automatic temperature compensation is available when the connected probe contains a compatible temperature sensor.

PHP-31, 640S-1, 640S-2 and 640S-3 provide temperature measurement together with pH measurement.

The 640S-4, 640S-5 and 640S-6 do not contain a temperature sensor, so automatic temperature compensation is not available from those probes alone.

Sensor Sensitivity Display

The SK-650PH includes a sensor sensitivity display that helps indicate the condition of the connected pH electrode.

This can be used as a guide when deciding whether electrode cleaning, maintenance or replacement may be required.

Data Memory and PC Output

Up to 99 readings can be stored in the meter for later review. Stored pH data include the data number, pH value, temperature and time.

The SK-650PH also provides RS-232C output. An optional RS-232C cable is required for connection to a computer.

Standard Solutions

Cat. No.Standard Solution
6401-10 pH 4.01 phthalate solution, 500 mL
6402-10 pH 6.86 neutral phosphate solution, 500 mL
6404-10 pH 9.18 borate solution, 500 mL
6403-10 pH 10.01 carbonate solution, 500 mL

Typical Applications

  • Laboratory pH measurement
  • General liquid testing
  • Industrial sample testing
  • Research and development
  • Water and solution checks
  • Quality-control laboratories
  • Tank measurements with immersion probe
  • Flat-surface pH measurements
  • Small-volume samples
  • Test-tube measurements

Before Selecting a Probe

Confirm the following:

  • Expected pH range
  • Sample type and chemical compatibility
  • Liquid, surface or very small sample measurement
  • Need for automatic temperature compensation
  • Required immersion depth
  • Required cable length
  • Whether the sample requires a specialised electrode

The SK-650PH meter itself has a display range of 0.00 to 14.00 pH, but the actual measuring range and accuracy depend on the connected probe.

Calibration Note

Sato lists calibration service as available for the SK-650PH. JCSS-accredited calibration is not available for this model. Suitability for regulated, certification or transaction applications should therefore be confirmed according to the user's measurement requirements.



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