Monitoring apparatus for measuring particles suspended in liquid and for measuring the opacity of the liquid

• US 3,892,485 A
• Filed: 05/06/1974
• Issued: 07/01/1975
• Est. Priority Date: 05/06/1974
• Status: Expired due to Term

• Current Assignee: Amespace Incorporated
• Original Assignee: Norbert John Hester, Robert Bruce Merritt
• Inventors: Merritt, Robert Bruce, Hester, Norbert John
• Primary Examiner(s): Demeo, Palmer C.
• Application Number:
  US05/467,286
• Time in Patent Office: 421 Days
• Field of Search: 356/208,103,70 250/573,574
• US Class Current: 356/339
• CPC Class Codes: G01N 21/532 with measurement of scattering and transmission

Abstract

This invention relates to a portable monitoring apparatus for detecting wear particles which may be suspended in a liquid such as the lubricating oil of turbine engines and for detecting changes in the opacity of the oil. The oil sensor which may be inserted directly into the lubrication system of the engine consists of a sensor assembly having a chamber or U-shaped channel into which the oil flows. A light emitting, solid state lamp and a first photodiode are positioned on opposite sides of the channel or chamber so that the photodiode measures the attenuation of the light passing through the oil. A second photodiode is placed at a 90* angle to the light beam to measure light scattered by wear particles suspended in the oil. The signals from the two photodiodes are processed and displayed to provide an indication of the degree of attenuation of the light beam due to changes in opacity and of the magnitude of the scattered light which is a measure of the amount of wear debris in the oil. The opacity of the oil is measured without directly sensing the degree of light attenuation. That is, illumination of the scatter field of view and of the first photodiode is kept constant by varying the light emission from the lamp through a closed loop control system. The change in the lamp supply voltage necessary to maintain illumination level constant is thus a measure of the light attenuation due to changes in opacity. Furthermore, by maintaining a constant illumination level in the scatter field of view, errors in the scatter output indication are avoided. That is, in the absence of a constant light level in the scatter field of view, the amount of light scattered by a given concentration of particles varies with the opacity of the oil. As opacity increases, attenuation increases and the scattered light decreases. This results in decreased output from the scatter photodiode giving an erroneous indication that there has been a reduction in the particle concentration whereas the actual reduction of the output from scatter photodiode is due to the darkening color of the oil. By maintaining constant illumination in the scatter field of view through a closed control loop which varies the light output of the lamp, an accurate measurement of the particle concentration is made possible by eliminating errors which are brought about by changes in the opacity of the oil.

Claims

1. A monitor for simultaneously measuring the particle concentration in a liquid and the opacity of the liquid, comprising, a. a body adapted for immersion in a liquid and having means defining a passage for receiving a liquid to be monotored;

b. a source of radiation positioned in said body for transmitting a beam of radiant energy through said liquid in said passage;

c. a first radiation detection means for receiving radiant energy transmitted through said liquid;

d. a further radiation detection means positioned for receiving radiation scattered by particles suspended in said liquid;

e. means responsive to output from said first radiant energy detection means for varying the output from said radiation source as a function of the transmission characteristics of said liquid to maintain the intensity of the radiation in the scatter field of view of said further radiation detection means and at said first radiation detection means constant with changes in the opacity of said liquid;

f. means to measure the transmission characteristics of said liquid indirectly including means for producing a signal in response to the change in output from said radiant energy source as a measure of the opacity of the liquid;

g. means responsive to the output from said further radiation for measuring the particle concentration.

2. The monitor according to claim 1 wherein the means for varying the output from said radiation source includes a control loop coupled between said first radiation detection means and said source of radiation for varying the supply voltage to said source.

3. The monitor according to claim 2 wherein said control loop includes a voltage supply for said source of radiation, means responsive to the output from said first radiation detecting means for varying the magnitude of the supply voltage to said source as a function of the attenuation in said liquid to maintain the illumination of the said scatter field of view and at said first radiation detector constant with changes of opacity of said liquid.

4. The monitor according to claim 3 wherein said loop includes means to produce a control signal as a function of the attenuation in said liquid, means for varying the magnitude of said supply voltage in response to said control signal to vary the output from said radiation source with changes in opacity.

5. The monitor according to claim 4 including means for measuring the supply voltage to said radiation source to provide a measure of the transmission characteristics and opacity of said liquid.

6. The monitor according to claim 2 wherein said source of radiation is a solid state, infrared emitting diode for transmitting infrared radiation through oil to measure the opacity of the oil and the particle concentration in said oil.

7. A monitor for indirectly measuring the opacity of a liquid comprising, a. a body adapted for immersion in a liquid and having means defining a passage for receiving liquid to be monitored;

b. a source of radiation positioned in said body and communicating with said passage for transmitting a beam of radiant energy through said liquid;

c. radiation detection means for receiving radiant energy transmitted through said liquid;

d. means for varying the output from said source of radiation as a function of the transmission characteristics of said liquid including a control loop for varying the supply voltage to said radiation source in response to the output of said detection means to maintain the illumination at said detection means constant with changes in the opacity of the liquid; and

e. means to measure the supply voltage to said radiation source to provide an iNdication of the transmission characteristic and opacity of said liquid.

8. The monitor according to claim 7 wherein said source of radiation is a infrared emitting diode for transmitting infrared radiation through oil to measure the opacity of the oil.