Oil in Water | Part III | |
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The I to E Converter also has an input offset trimpot R3, which function is to offset the signal baseline slightly, to clean up the log amplifier outputs signal. Its adjustment will be covered under Section 7.1.5.
7.3Set Up of the Logarithmic Amplifier
The amplifier is inverting and continuously takes the logarithm of the output signal of the second amplifier. The output can be observed by connecting the scope probe to
The correct wave shape must have a rounded negative going pulse which is the signal and a flat topped positive pulse which depicts saturation of the log amplifier.
No distortions or oscillations are permitted on the rounded peaks. When the positive going pulse is not flat or is distorted, adjust the offset adjustment trimpot R3 on the I to E Converter. However, adjust no more than required to just obtain a flat positive pulse. Over adjusting can result in losing part of the amplifier’s capability to operate in the second decade of its logarithmic operating range and will affect the accuracy of analysis for high concentrations of the component of interest where the measuring pulse can become very short. Saturation of the log amplifier’s output is due to the amplifiers incapability to take the logarithm of the slightly negative baseline.
7.4The Inverting Amplifier
The amplifier is inverting and has a gain of 1. Its function is to invert the output signal of the logarithmic amplifier and to act as a buffer between the logarithmic amplifier and the reed switch and integrators. To observe the output of the inverter, connect the scope probe to
The wave shape must be a duplicate of that observed on
7.5The Integrated Reference and Measuring Signals
Teledyne Analytical Instruments | Part III: |
