* Sensitivity display function
Available to check the status of deterioration of sensor.  Useful to determine the timing of maintenance
* Stability display function
Easy to find the measuring values being stabilized
* Auto temperature compensation
Available to produce more accurate measurements
* Measured value, date and time are simultaneously displayed
* Available to calibrate at one to three points
Selectable calibration points (at 25°C) among pH4.01, pH6.86 and pH9.18 or pH10.01
* Data memory function
The memory capacity is max. 99 data
* Measured data can be transmitted to a PC with RS-232C output
 (RS-232C cable is optional and can be purchased separately)
* Sensor arm is attached
Convenient to use a stirrer or like.
* Various probes are provided. Available to select the suitable probe to your required application

at. No. 6427-00
Product Desktop type  PH Meter
Model SK-650PH
Display range pH 0.00pH to 14.00pH
Temp. -6.0 to 82.0°C
mV ±2002mV
Repeatability pH ±(0.01+1digit)pH
Temp. ±(0.1+1digit)°C
Accuracy is different depending on the probe connected.
Resolution pH 0.01pH
Temp. 0.1°C
mV 0.1mV  at -199.9 to +199.9mV 1mV at other
Sampling approx. 1 sec.
Operation ambient 5°C to 40°C, less than 95%rh (no condensing)
Storage ambient -10°C to 50°C (no condensing)
Power requirement AC adapter 9VDC (attached)
Materials Body, sensor arm: ABS resin
Dimensions (W)215×(H)58×(D)170mm (exclusive of arm)
Weight 915g (exclusive of arm)
Accessories Sensor arm 1 set, AC adapter 1 pc. Manual

Standard Probe No. 6400-30 Model PHP-31 for SK-650PH and SK-620PHII Specifications 
  pH Temperature
Measurig range 0.00 to 14.00pH 0.0 to 50.0°C

Measuring accuracy

±0.28pH (0 to 2pH)
±0.08pH (2 to 12pH)
±0.38pH (12 to 14pH)
±0.3°C (at 20 to 30°C)
±0.5°C (at other range)
Sensing element Glass electrode (lead-free) Thermostor
Internal liquid
12 dia. x (L)135mm   cord length: approx. 1m (weight: approx. 72g)


[640S Series pH Optional Probes]
Applications for General purpose for immersion for High-alkali for Flat surface for Test tube for Minute amount
Cat. No. No.6424-00 No.6425-00 No.6425-10 No.6425-20 No.6425-30 No.6425-40
Model 640S-1 640S-2 640S-3 640S-4 640S-5 640S-6
Measuring range pH 2.00 to 13.00pH 2.00 to 14.00pH 2.00 to 13.00pH
Temp. 0 to 50°C -
Accuracy pH ±0.03pH
Temp. ±0.5°C -
Sensing elements pH Glass electrode
Temp. Thermistor -
Liquid junction Sleeve type Ceramics type Sleeve type
Internal liquid 3.3mol/L KCl (replenishable) 3.3mol/L KCl (non-replenishable) 3.3mol/L KCl (replenishable)
Usable temperature range 0.0 to 50.0°C 15.0 to 50.0°C 10.0 to 50.0°C
Materials Electrode holding tube Glass (Lead free) PVC Glass (Lead free)
Cord PVC
Dimensions Sensor section approx. 12 dia. × L156mm  34 dia. × L137mm 12 dia. ×L159mm 12 dia.×L156mm Ø6×L190mm
(sensor L=270mm)
(sensor L=148mm)
Cord length 1m 3m 1m
Weight 78g 460g 76g 69g 63g 59g
Accessories Glass electrode cap 1 pc.
Glass electrode protection cap 1 pc
Replenisher liquid (35ml) 1 pc.
Instruction manual 1 pc.
Glass electrode cap 1 pc.
Glass electrode protection cap 1 pc
Instruction manual 1 pc.
Glass electrode cap 1 pc.
Glass electrode protection cap 1 pc
Replenisher liquid (35ml)  1 pc.
Instruction manual 1 pc.
Glass electrode cap 1 pc.
Replenisher liquid (35ml) 1 pc.
Instruction manual 1 pc.
• Available to change the cord length in 640S-1 and 640S-2 probe at option
• Temperature probe for temperature compensation is not built in 640S-4, 640S-5 and 640S-6 probes
• In the 640S-2 probe, standard solutions attached with SK-620PHII are not usable. Separately purchase the optional solutions.


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