Comparator circuit for automatic analysis apparatus

• US 3,961,898 A
• Filed: 01/14/1975
• Issued: 06/08/1976
• Est. Priority Date: 01/14/1975
• Status: Expired due to Term

• Current Assignee: The United States Of America As Represented By The Secretary Of The Army
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Wardlaw, Stephen C., Neeley, William E., Swinnen, Maurice E. T.
• Primary Examiner(s): Serwin, R.E.
• Application Number:
  US05/541,033
• Time in Patent Office: 511 Days
• Field of Search: 23/230 R, 23/259, 23/253 R, 356/181, 356/204, 356/229, 346/33 A, 235/151.35
• US Class Current: 422/62
• CPC Class Codes: G01J 1/18 using comparison with a reference electric value
• CPC Class Codes: G01N 35/08 using a stream of discrete samples flowing along a tube system, e.g. flow injection analysis

Abstract

The invention concerns an automatic continuous-flow fluid analyzer of the pe wherein a stream of fluid, segmented by air bubbles or other separating medium inert to the fluid to be analyzed, passes through a colorimeter flow cell. The bubble artifact is eliminated from the photoconductor signal while allowing the signal produced from the fluid segment to remain intact. This is accomplished by means of a signal comparator which operates as a digitally controlled differentiator, but could alternatively be a purely analog differentiator. The signal comparator through continual signal comparisons momentarily samples and stores a photoconductor output.

For a finite period of time, the stored value is compared with all subsequent succeeding photoconductor output signals. If any signal that follows varies outside a preset range from the stored value, the comparator logic concludes that an air bubble is passing and the output to the recorder is not changed. The recorder continues to record from the signal in the memory means at all times. If the signal that follows remains constant as compared to the stored value, the comparator logic concludes that a fluid segment is in the flow cell and the signal at that time is transferred to the memory means and to the recorder.

Claims

1. In a continuous-flow fluid analyzer having a colorimeter flow cell and means for conducting fluid segmented by a substance inert to the fluid through the colorimeter flow cell, the improvement comprising:

a. sampling and storing circuit means receiving signals from the flow cell;

b. memory and recording means connected to and receiving signals from said sampling and storing means;

c. differentiator circuit means connected to said sampling and storing means and to said memory and recording means for limiting voltages received by said memory and recording means;

d. logic circuit means including interconnected repetitive pulse generating means, counter means, decoder means and flip-flop circuit means connected to said sampling and storing circuit means and said memory and recording circuit means, said differentiating circuit means selectively controlling said flip-flop circuit means, whereby a selected output signal from said colorimeter flow cell is stored in said storing circuit means and compared with succeeding signals from said flow cell during a cycle of repetitive pulses, said flow cell output signals conducted to said memory and recording circuit means selectively when the voltage difference of said succeeding and stored pulses does not exceed limiting voltages set by said differentiator circuit means and said flip-flop circuit means is activated to permit recording of said selected flow cell output signals.

2. A digitally controlled signal comparator for use in combination with a continuous-flow fluid analyzer having a colorimeter flow cell with a photodetector and means for conducting fluid segmented by a substance inert to the fluid through the colorimeter flow cell, said signal comparator including interconnected means for sampling and storing the output signal of the photodetector, differentiator circuit means for limiting voltages of output signals from said photodetector to be recorded, a repetitive pulse generator means, a decade counter, a BCD-to-decimal decoder, memory and recording means for the output of said signal comparator, and a flip-flop circuit means whereby without interruption to said recording means an input signal is selected from the output of said photodetector, stored by said storing means for a period determined by the cycle of said decade counter, pulsed by said pulse generator means, converted to analog notation by said decorder and recorded upon activation of said flip-flop circuit means by said differentiator means.

3. A digitally controlled signal comparator as recited in claim 2 wherein said flip-flop circuit means is enabled by the pulse succeeding said selected pulse emitted by said BCD-to-decimal decoder during the period of a cycle determined by said decade counter.

4. A digitally controlled signal comparator as recited in claim 2 wherein said sampled and stored signal is continuously compared with all subsequent signals for the finite time period of pulses following the pulse enabling said flip-flop circuit means, said recorded pulses being limited by output of said differentiator circuit means which will maintain the preset activation of said flip-flop whereby only signals of predetermined value will be transmitted to said memory and recording means.

5. A digitally controlled signal comparator for selectively recording without interruption the physical characteristics of a fluid material being tested comprising:

a. sampling and storing means receiving the raw input signal;

b. memory and recording means connected to and receiving signals from said sampling and storing means;

c. differentiator circuit means connected to said sampling and storing means and to said memory and recording means for selectively limiting voltages received by said memory and recording means;

d. logic circuit means including interconnected repetitive pulse generating means, counter means, decoder means and flip-flop circuit means connected to said sampling and storing circuit means and said memory and recording circuit means whereby said raw input signal is selected, stored by said storing means for a period determined by the cycle of said decade counter pulsed by said pulse generator means, converted to analog notation by said decoder and recorded upon activation of said flip-flop circuit means by said differentiator means if said raw input signal is within said selected voltage limits of said differentiator.