Tophit H CPS471/CPS471D
Hauser
3
Important characteristics of
Tophit CPS 471
• Resistance to breaking
This is the most obvious feature of the sensor. The complete sensor technology is embedded in a PEEK shaft.
Only the highly resistant isolator layer and the reference have direct contact with the medium.
• Acid or alkaline errors
A further, important benefit compared with the glass electrode is the considerably reduced number of acid
or alkaline errors in extreme pH ranges. In contrast to glass electrodes, practically no foreign ions can build
up at the ISFET gate. The measuring error of < 0.01 pH (between pH 1 and 13) at 25°C (77 °F) is near by
the detection limit.
The figure below shows the acid or alkaline error of the ISFET between pH 1 and 13 and the comparison to
the glass electrode (two different pH glasses) at pH values 0.09 and 13.86.
a0003867-en
Fig. 3:
Comparison of acid and alkaline errors
• Measurement stability and sensor response time
The ISFET response times are very short over the whole temperature range.
With the ISFET sensor, there is no (temperature-dependent) equilibrium setting as in the source layer of a
pH glass of a glass electrode. They can also be used at low temperatures without a deceleration in response
time.Large and fast temperature and pH value fluctuations have a smaller effect on the measuring error
(hysteresis) than with a glass electrode, as there is no stress exerted on the pH glass.
• Reference system
The integrated reference electrode of the sensor is a double-chamber reference system with a bridge
electrolyte. The benefits are an efficient and stable contact between the diaphragm and the reference lead,
and the extremely long poisoning path. The bridge electrolyte is highly resistant to temperature and pressure
changes.
pH (25 °C)
D
pH
1 M NaOH
1 M HCl
E+H ISFET
pH 1 … 13
Glass 1
Glass 2
-0.2
0.0
0.2
0.4
0.6
0.8
