Chapter 2 — The pH/mV Amp
13
You can shift and stretch the vertical Amplitude axis to make the best
use of the available display area (see the Input Amplifier dialog in the
Chart Software Manual
for further details). Changes made here update
settings in the main window of the program.
Setting the Range
Use the Range pop-up menu to select the input range or sensitivity of
the channel — the combined range of the pH/mV Amp and the
e-corder. Changing the range in the pH/mV Amp dialog box is the
equivalent to changing it in the Chart or Scope window (all dialog box
changes are made in the main window on clicking the
button).
At 25 °C a range of 59 mV corresponds to a range of approximately
one pH unit. This relationship is used in
Table 2–1
which shows the pH
ranges corresponding to the pH/mV Amp range settings. For general
pH measurements, a range of 500 mV should be used, while the
200 mV range is suited for biological pH monitoring.
Filtering
The pH/mV Amp has three low pass filter settings of 2 kHz, 50 Hz and
10 Hz. The low pass filter will remove high frequency noise. pH and
ion selective electrodes have a slow response time, usually in the order
†
Resolution is 16 bits, or 0.0015%, of range setting with Chart and Scope software.
* This range will be limited by the pH electrode
Range setting (mV)
Resolution
†
(µV)
Range (pH)
Resolution (pH)
±500
15.6
–1.5 to 15.5*
< 0.001
±200
6.25
3.6 to 10.4
< 0.001
±100
3.13
5.3 to 8.7
< 0.001
±50
1.56
6.2 to 7.8
< 0.001
±20
0.625
6.7 to 7.3
< 0.001
Table 2–1
pH/mV Amp range
settings corresponding to
pH ranges
Summary of Contents for e-corder pH/mV Amp
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