Difference between revisions of "Raw signal of the oxygen sensor"

Revision as of 03:33, 15 August 2010

For trouble shooting purposes of the polarographic oxygen sensor (POS), for choosing an appropriate gain setting (default is Gain 2), but also to understand how the O2k actually works, it is helpful to observe the raw signal (on-line or off-line).

Observing the Raw Signal

Depending on your DatLab version, a predefined layout called „B Trouble shooting“ is in the „Graph layout“ menu. If not, you can easily generate this Graph layout. To do so, take the following steps in DatLab [MiPNet12.07]:

From the main menu select “Layout” menu and choose „1 Calibration Exp. G3-Temp“
From the main menu select „Graph“ / „Select Plots“, by default you will see the „plots“ tab from the drop down menus for the oxygen signals. Select „O2 raw signal“ instead of „O2 concentration“ for both chambers.
Select the „scaling“ tabs: adjust the scaling for the oxygen signal to 0 – 10 Volt (Start at 0, Range 10)
At the bottom of the window insert a name for the new layout („B Trouble Shooting“); press „Save Graph Layout“.

Remember to select the period of the experiment your are interested in or select “Graph” / “Autoscale Time Axis” to view the entire experiment. The maximum signal is 10 volt. Above 9.99 V, the amplifyer is in the saturation range, the apparent signal will remain constant at this value, and the flux will appear to be zero. The raw signal can be modified by choosing an appropriate gain setting. We recommendate a gain of 2 as a default for experiments at and below air saturation, to avoid reaching the upper 10 volt limit without noticing. Typical recorded voltages at air saturation, in pure water or experimental media, should be

at Gain 8: offsale ( “9.99V”)
at Gain 4 : ca. 8-10 V (don't use at air saturation, especially if your lab is situated at or near sea level)
at Gain 2: ca. 4-5 V
at Gain 1: ca. 2 V

The actual value of the raw signal at air saturation (during calibration) depends on experimental temperature, barometric pressure, and the sensitivity of the individual POS. At or near sea level higher values are recorded than at higher altitudes. The raw signal is converted to oxygen concentration [µM or nmol/ml] or partial oxygen pressure [kPa] by calibration of the POS [MiPNet12.08]. Each gain requires a separate calibration of the oxygen signal. Therefore, after changing the gain you should not only perform a calibration at air saturation (as always before an experiment), but also a new zero calibration. Oxygen concentrations that are recorded after proper calibration are independent of the gain setting used during calibration.

@@ Line 1: / Line 1: @@
-For trouble shooting purposes, for choosing an approbate gain setting, but also to understand how the oxygraph actually works, it is helpful to directly observe the raw signal, not only in (in the on-line mode) as a momentary value in the O2k signal line but also as a plot.
+For trouble shooting purposes of the polarographic oxygen sensor (POS), for choosing an appropriate gain setting (default is Gain 2), but also to understand how the O2k actually works, it is helpful to observe the raw signal (on-line or off-line).
 == Observing the Raw Signal ==
-Depending on the delivery date of your datlab version you will either find a predefined layout called „B Trouble shooting“ in your „layout“ menu, or you can easily set up this view yourself as a layout. To set up this view manually:
+Depending on your DatLab version, a predefined layout called „B Trouble shooting“ is in the „Graph layout“ menu.  If not, you can easily generate this Graph layout. To do so, take the following steps in DatLab [[http://www.oroboros.at/index.php?o2k-datlab-guide MiPNet12.07]]:
-from the main menu select “Layout” menu choose „1 Calibration Exp. G3-Temp“
+*From the main menu select “Layout” menu and choose „1 Calibration Exp. G3-Temp“
-from the main menu select „Graph“ / „Select Plots“, by default you will see the „plots“ tab
+*From the main menu select „Graph“ / „Select Plots“, by default you will see the „plots“ tab from the drop down menus for the oxygen signals.  Select „O2 raw signal“ instead of „O2 concentration“ for both chambers.
-from the drop down menus for the oxygen signals select „O2 raw signal“ instead of „O2 concentration“ for both chambers
+*Select the „scaling“ tabs: adjust the scaling for the oxygen signal to 0 – 10 Volt (Start at 0, Range 10)
-select the „scaling“ tabs: adjust the scaling for the oxygen signal to 0 – 10 Volt (Start at 0, Range 10)
+*At the bottom of the window insert a name for the new layout („B Trouble Shooting“); press „Save Graph Layout“.
-at the bottom of the window insert a name for the new layout („B Trouble Shooting“ is a good idea)
-press „Save Graph Layout“
 Remember to select the period of the experiment your are interested in or select “Graph” / “Autoscale Time Axis” to view the entire experiment.
-The maximum signal is ten volt. If this current is reached the signal will stay there and therefore the flux will appear to be zero. The raw signal can be modified by choosing an approbate gain setting. We recommendate a gain of 2 for experiments at or near air saturation, to avoid reaching the 10 volt without noticing.
+The maximum signal is 10 volt.  Above 9.99 V, the amplifyer is in the saturation range, the apparent signal will remain constant at this value, and the flux will appear to be zero.  The raw signal can be modified by choosing an appropriate gain setting.  We recommendate a gain of 2 as a default for experiments at and below air saturation, to avoid reaching the upper 10 volt limit without noticing.
-Typical recorded voltages at air saturation, in pure water should be
+Typical recorded voltages at air saturation, in pure water or experimental media, should be
+* at Gain 8: offsale ( “9.99V”)
+* at Gain 4 : ca. 8-10 V (don't use at air saturation, especially if your lab is situated at or near sea level)
+* at Gain 2: ca. 4-5 V
+* at Gain 1: ca. 2 V
- at gain 8: offsale ( “9.99V”)
+The actual value of the raw signal at air saturation (during calibration) depends on experimental temperature, barometric pressure, and the sensitivity of the individual POS. At or near sea level higher values are recorded than at higher altitudes.
- at gain 4 : ca. 8- 10 V (don't use at air saturation, especially if your lab is situated at or near sea level )
+The raw signal is converted to oxygen concentration [µM or nmol/ml] or partial oxygen pressure [kPa] by calibration of the POS [[http://www.oroboros.at/index.php?o2k-o2calibration MiPNet12.08]].  Each gain requires a separate calibration of the oxygen signal. Therefore, after changing the gain you should not only perform a calibration at air saturation (as always before an experiment), but also a new zero calibration.  Oxygen concentrations that are recorded after proper calibration are independent of the gain setting used during calibration.
- at gain 2: ca. 4-5 V
- at gain 1: ca. 2 V
-The actual value depends on the sensitivity of the individual sensor and the barometric pressure. Thus, labs situated at or near sea level will record higher values than labs situated in higher altitudes and gain 4 is to high for them at air saturation.
-The raw signal is converted into a oxygen concentration by the calibration. Each gain requires a separate calibration of the oxygen signal. Therefore after  changing the gain you should not only perform a calibration at air saturation (as always before an experiment), but also a new zero calibration. Oxygen signal that have been obtained after proper calibration are independent of the gain setting. Therefore oxygen concentrations (and fluxes) that have been recorded at different gain settings can of course be used together.
 {{#set:keyword=sensor}}
 [[Category:Troubleshooting]]