JPS631961A - Remote sensor for conductivity - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A flow path means having an inlet and an outlet and two flow paths between the inlet and the outlet thereby defining a fluid loop; a first flow path having a through hole; An excitation transformer comprising a core and a winding around the first core, the first core surrounding a portion of the flow path means and the fluid loop in the means. a sensing transformer comprising: a second core having a through hole; and a winding around the second core; A sensing transformer that partially surrounds the loop; and a dialysate preparation and supply device.

13. The dialysate preparation/supply device according to claim 12, wherein the first core and the second core are annular.

3. Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a system for remotely sensing the conductivity of a fluid flowing in a conduit, and particularly for sensing the conductivity of a dialysate in a dialysate preparation/supply machine. related to things.

[Conventional technology]

The conductivity of the dialysate in a dialysate conditioning and feeding machine is usually measured by a sensor immersed in the dialysate in the conduit and is subject to long-term drift due to membrane morphology, deposits on the electrodes, or other shortcomings. Easy to accept.

Electrodeless conductivity sensors, such as those available from Great Lakes Instrument Inc. (Milwaukee, Wis.), have been used for water quality and treatment control. In one of these sensors, the conductivity of the fluid flowing in the conduit is determined by the conduit G (with a connected fluid loop and two transformers coupled with the loop). -1 current is induced in a transformer on one side of the fluid loop V, the current induced in the other transformer by the current in the fluid loop is measured, and the conductivity in the fluid is determined by the resistance , by using the current and voltage relationships to determine ``V'' and ``ft''.

[Summary of the invention]

General V This invention provides a method for converting the excitation transformer in a two-transformer/fluid loop type conductivity remote sensor by using coplanar annular ferrite cores for the excitation transformer and the sensing transformer. One characteristic that provides reduced leakage coupling between the transformer and the sensing transformer is characterized.

In a preferred embodiment, the desirably low ratio of the length of the fluid loop to the cross-sectional area of the fluid extends through the two annular magnets to the first connection and the second connection. T7
C-Z by a fluid flow conduit having two circular sections connected to the C-Z, the inner diameter of the annular magnet and the winding around said magnet being approximately equal to the diameter of said circular conduit section. , Mi + (approximately equal to the length of the diameter of the annular magnet and the winding around the magnet. 111
Hold the vessel in place.

To another characteristic]? According to the present invention (4-Generally, the current excitation transformer of the 2-transformer/fluid loop type conductivity can be controlled by a digital timer and a solenoid knob.
It further comprises driving with square wave excitation 1b''F3.

In a preferred embodiment, it is connected to both the output of the excitation transformer (which is high-filter wound and one of the solenoid knobs) and the output of the second transformer. There is a current-to-voltage converter, an AC amplifier, and a synchronous detector connected to the transformer, and there are additional windings around the transformer for use in calibrating the sensor.

In another aspect, the present invention generally provides an electrodeless method for sensing the conductivity of dialysate. It is characterized by its use as a power outage rate sensor.

Other advantages and features of the invention will be apparent from the following description of the preferred embodiment and from the claims. A conductivity cell 10 is shown comprising a fluid flow conduit 12, an excitation transformer 14, and a sense transformer 16. The excitation transformer 14 and the sense transformer 16 each have a 1 m Idalko core I8 and a wire 20 wound around the core. Installed in the dialysate flow path of a dialysate preparation and feed machine of the general type described in Patent No. 4,371,385 downstream from the point along the dialysate feed conduit where the concentrate and water are mixed. and is connected to a processor for controlling the addition of concentrate to the water.

Channel 12 is person I'l 22, lit I] 24,
It has a circular conduit section 26.28 (through the transformer 14.16) and a connection between the conduit sections 26.28: 30.32.

The extension 1Nts31 is aligned with the connection part 30 and has a circular force extending from the pipe part 26 to the population 22.Extension part 3
5 is a connection; (aligned with 2 and extending out of the circular conduit section 28 []24-\); the connection 30.32 has a flat outer surface and a (4l-4).As best seen in FIG. is close to the dimension of the inner diameter of the l-roidal core, thereby providing the largest practical cross-sectional area for fluid flow paths allowed by the dimensions of the l-roidal core.1
However, the height of the circular conduit part is slightly thicker than the thickness of the toroidal core 18 and the windings and wires of the core 7, and the height is different.
The distance between transformer 1 and transformer 6 is small. (1)
The length of the first connection between the circular conduit part 26 and the circular pipe part 28 is the length of the toroidal core and the winding ifl on the 6-core core (slightly larger than the self-made one). 1. :
, > One device! -J, connection 30.32 and circular conduit 26.28! Flow loop of 5 bodies (given by two): The ratio of the length of 38 (-dotted chain line in Figure 3) to the cross-sectional area of the flow path is set to a low value, and as a result, good sensitivity is provided. do. Although it would be possible to physically bring transformers so close together that the windings on one core overlap and even touch the windings on the other core, in practice It is impossible. This is because it tends to increase the probability of leakage coupling between transformers.

As can be seen in FIG. 5, the channel 12 is made from two identical parts 34.36 which are solvent bonded after inserting the transformer 14.16 between them.

Referring to FIG. 6, the figure shows the excitation signal being transferred to the excitation transformer 1.
4 and receives a signal from a sensing transformer 16 that is related to the conductivity of the fluid. The transformer 14 is connected to an oscillator 39 and a drive circuit 40 on the left side of the figure.
It is connected to receive a 0 KHz square wave excitation signal. On the right, the sensing transformer 16 is connected to the amplifier 58.60
．． 62 and 64 (LF 347), respectively, to a current-to-voltage converter 42, an AC amplifier 44, a synchronous detector 46, and a filter/buffer 48.

The oscillator 39 includes a timer 41 (7555) and a flipflop 43 (74HC74). Both the "true" and complementary outputs of the flip-flop 43 are connected to the drive circuit interface 45 (7545]), the "true" and complementary outputs of the interface being connected to the transformer 14. . flip flop 43
The "true" output (Q) of is also connected to the sync detector 46 by a shortened line 50.

The excitation transformer 14 is a bifilar transformer with 43 turns. The number of turns of the sensing transformer 16 is 89. Each of the excitation transformer 14 and the sensing transformer 16 includes a
The winding 52.54 is wound once, and the winding 52.5
4 is connected to calibration pin 56, which is connected to a resistor used to calibrate the device. The numerical values of the remaining parts in FIG. 6 are as follows.

Parts price or number C80,00
56 CIOO,001 C1,C2,C5,C6,0,1 C13,C14,C15 C90,47 CI 2 , C161,0 C3,C4,C710,0 C111oopf Resistance R613,0 R13100,0 R100,28K R7,R112 , 4K R410, 2K R9, R1214, 0K R1, R223, 7K R82B, 0K R349, 9K R141000K R5274, OK Transistor Ql 2N3904
In operation, dialysate flows into inlet 22 and exits loop 38.
through to outlet 24. The dialysate then fills all fluid flow paths between inlet 22 and outlet 24, creating a fluid loop that is coupled to transformer 14,16. The conductivity cell 10 is mounted so that the flow path through the connections 30, 32 makes an angle of 45° to the horizontal, so that air bubbles (which distort the measurements) stagnate. There are no corners. In this way, the air bubbles are also expelled.

Oscillator 39 provides a 10 KHz square wave that is applied to excitation transformer 14 by drive circuit 40 .

Square waves are advantageous because they are easily generated from cheap components, give constant amplitude, and do not need to be controlled like sine waves. Drive circuit 40 increases the square wave voltage received from oscillator 39 from a logic level of 5V to 12V.

Excitation transformer 14 induces a current in fluid loop 38 that is sensed by sense transformer 16 . ,
Electricity induced in transformer 16 i'ik +4 loop 38
(1) Medium no.ift□L'll\r\ratio IC proportional s, 4, transformer 16 is contin day no r'J, V ri amplification i+S 5
Capacitively coupled to 8, tl. DCAC offset for child ≦111! Now, only Senyumi is amplified! Shiru 1,
The output of amplifier 58 is applied to Δ in loop 38, which is proportional to the female current rate ('). Contently-CI2
1) The amplifier 60 is used to prevent C offset 11) 1) The amplifier 60 only amplifies AC voltage 4 and 6
, The synchronous detector 46 connects the AC Ichikawa of the amplifier 44 to 111.
In addition to converting it into the output of the current city pressure, it also removes the uneasy frequency 4. When the transistor Q1 is turned on, driven by the Flinob flop 4:3, the transistor Q1 acts as a ground to ground and the amplifier 62
When an inverting amplifier with a gain of and (operating at ),
AC, output of amplifier 44 (J negative, synchronous 4 output device 4
6 produces an output of l-. When the transistor Q1 is turned on, the transistor Q1 acts as a circuit, and the amplifier 62 has a gain of -1. At this time, the output of the AC amplifier 44 is 44, and the synchronous detection 'AI' and 4 outputs of 46 are generated again.

Synchronization (the output of step 11 and 16 is connected to resistor 14 through L7:
I am charging 160 meters. There is no intervening frequency other than 10 KHz, and over a long period (・ζ), the constant component and the negative component are equalized by X17.
], OJ (ilz's frequency count - only one bow) 1~
So content C, 1, 6 are filled with 12, fill/buffer 48 Masunaka Hatatsu χ6・1 is 'IJ'1'! pass

Fill 1 / Buffer 18σ) Output It conductivity (J (proportional direct 1'Δv' city FT-. Facial direction k fl] pressure (Soil, body j%l 'f, !I-H4th, 371.385
4-VC note j-1t; sa h -j-, iru general (7)
7jl, 1 dialysate preparation No assignment of feeder a) ta1\/
) is converted to JL1('), via a digital processor (not shown), and a 4/D converter (not shown). Ru.

The circuit of FIG.
The output of the filter/buffer 18 may be calibrated by comparing the output of the filter/buffer 18 with the known resistance of the resistor (by coupling the transformer 14.16 to the claws through a single winding 52.5.1).

Other examples Other embodiments of the invention are within the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conductivity cell according to the invention. FIG. 2 is a partial cross-sectional view of the cell of FIG. 1. FIG. 3 is an elevational view of the cell of FIG. FIG. 4 is a longitudinal cross-sectional view of the cell shown in FIG. 1 taken along section 4--4 in FIG. FIG. 5 is a cross-sectional view of the cell of FIG. 1. FIG. 6 is a diagram of an excitation/sensing circuit connected to the cell of FIG. 1. 10: Conductivity cell 12: Conduit 14: Excitation transformer 16: Sensing transformer 18 Nidroidal core
2o: Electric wire 22: Entrance 24: Exit 26.28
: Conduit 30, 32: Connection part 33: Inner surface 38
: Fluid flow loop 39: Oscillator 4o: Drive circuit 41: Timer 42 Two current-voltage converter 43:
Flip-flop 44: AC amplifier (1'/) 45: Interface, 16. Synchronous detector 48゛ filter/buffer 5o, wire 52.54: winding
56: Calibration pin 58.60.62.64: Amplifier (1B)

Claims (1)

[Scope of Claims] 1. A cell for remotely sensing the electrical conductivity of a fluid passing therethrough, comprising means for defining a fluid flow path in a supply pipe, the inlet and the outlet, and the connection between the inlet and the outlet. an excitation transformer comprising: a first toroidal core having a through hole; and a winding around the first toroidal core. an excitation transformer in which the first toroidal core partially surrounds the flow path means and the fluid loop in the flow path means; and a second toroidal core having a through hole. A sensing transformer comprising a core and a winding around the second toroidal core, the second toroidal core connecting a portion of the flow path means and the fluid loop in the flow path means. a sensing transformer surrounding the second toroidal core, the plane of symmetry of the second toroidal core perpendicular to the axis of the through hole of the second toroidal core being a cell characterized in that it is coplanar with a plane of symmetry of said first toroidal core that is perpendicular to the axis of the through hole, thereby reducing leakage coupling between said excitation transformer and said sensing transformer; . 2. The channel means has two circular conduit sections of a first length and a second length measured between the centers of the two circular conduit sections, and the channel means has two circular conduit sections of a first length and a second length measured between the centers of the two circular conduit sections, and two connecting portions provided between the conduit portions, each of the conduit portions having an outer diameter approximately equal to an inner diameter of the toroidal core and the winding on the toroidal core, and wherein the first length is approximately equal to the inner diameter of the toroidal core and the winding on the toroidal core. The thickness of the toroidal core and the winding on the toroidal core is approximately equal, and the second length is approximately equal to the outer diameter of the toroidal core and the winding on the toroidal core. A cell according to claim 1. 3. The connecting portion has planar surfaces defining a circular flow path for fluid therein and opposing each other and delimiting portions of the toroidal core therebetween. Cell described in section. 4. A cell according to claim 2, characterized in that said channel means are comprised of identical parts, each said identical part having said connection part and half of each said circular conduit part. 5. In alignment with one said connection, there is a first extension extending beyond the inlet to one of said circular conduits towards said inlet, and in alignment with the other said connection; , there is a second extension extending in the opposite direction beyond the inlet to the other circular conduit towards the outlet, and the flow path at the connection and the flow path in the respective extension are continuous. 3. A cell according to claim 2, characterized in that the cell prevents foam from stagnation when mounted at an angle to the horizontal. 6. An apparatus for remotely sensing the electrical conductivity of a fluid passing therethrough, comprising means for defining a fluid flow path having a fluid loop, an exciting transformer each having a core surrounding a portion of the fluid loop; An apparatus comprising: a cell including a transformer for excitation; and a digital timer and a flip-flop connected to provide a square wave excitation signal to the transformer for excitation. 7. The apparatus of claim 6, wherein said excitation transformer is bifilar wound and connected to both the "true" output and the complementary output of said flip-flop. 8. The apparatus of claim 6 further comprising a current-to-voltage converter connected to the sensing transformer. 9. The device according to claim 8, further comprising an AC amplifier connected to the current-voltage converter. 10. Claim 6, further comprising one winding on the excitation transformer and one winding on the sensing transformer for use in calibrating the device. equipment. 11. Claim 10, further comprising a synchronous detector connected to the digital timer and the AC amplifier, the detector providing a DC voltage output.
Apparatus described in section. 12. A dialysate supply tube; and a flow path means for defining a fluid flow path in the supply tube,
having an inlet, an outlet, and two flow paths between the inlet and the outlet,
An excitation transformer comprising: a flow path means thereby defining a fluid loop; a first core having a through hole; and a winding around the first core, the first core A sensing transformer comprising: an excitation transformer surrounding a portion of the flow path means and the fluid loop in the means; a second core having a through hole; and a winding around the second core. a sensing transformer in which said second core surrounds a portion of said flow path means and said fluid loop in said means. 13. The dialysate preparation/supply device according to claim 12, wherein the first core and the second core are annular.