CN85105275A - Digital temperature meter - Google Patents
Digital temperature meter Download PDFInfo
- Publication number
- CN85105275A CN85105275A CN 85105275 CN85105275A CN85105275A CN 85105275 A CN85105275 A CN 85105275A CN 85105275 CN85105275 CN 85105275 CN 85105275 A CN85105275 A CN 85105275A CN 85105275 A CN85105275 A CN 85105275A
- Authority
- CN
- China
- Prior art keywords
- temperature
- circuit
- thermistor
- voltage
- display
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
A kind of digital temperature meter is made temperature-sensing element with thermistor, adopts the voltage-frequency translation circuit to overcome the non-linear shortcoming of thermistor; Thermistor by two replaceable different parameters of trimmer in the regulating circuit; Connect the influence of the transmission line of thermistor when utilizing self-balancing bridge to eliminate remote temperature measurement; Adopt BGD scale counting display circuit to make simple and reliable for structure.Therefore, thermometer of the present invention is a kind ofly to have that reading is directly perceived, the reflection dut temperature time is short, characteristics such as the wide and precision height of temperature-measuring range, and can carry out the New Digital thermometer of remote temperature measurement and temperature control.
Description
A kind of digital temperature meter.Belong to the thermometer of making of non-linear temperature-sensitive resistance.
The digital temperature meter that the general using thermistor is made has short, advantage such as resolution is high, reading is directly perceived of reflection dut temperature time.But thermistor exists two significant disadvantages, i.e. non-linear the and inconsistency of temperature-sensitive resistance, and the former has influenced temperature-measuring range and precision, and the latter has hindered the replacement of thermistor.China utilizes the temperature measurer that thermistor is produced at present, and its temperature-measuring range is-30 ℃～+ 30 ℃, and temperature measurement accuracy is ± 0.4 ℃; Abroad, temperature measurement accuracy is ± 0.1 ℃, and its temperature-measuring range is about 20 ℃.According to the clear 57-161628 introduction of day disclosure special permission communique, the digital temperature meter of forming by integrator, control loop, display circuit etc., its displays temperature value and log 1/ (Rt) are proportional, and the value relation of being inversely proportional to after in fact dut temperature T and thermistor Rt take the logarithm.Therefore, this and thermometer of design proportional according to dut temperature T and log 1/ (Rt) can only reach in an extremely narrow temperature range ± 0.1 ℃ measuring accuracy.In a wider temperature range, can't reach high like this precision.As for replacing the thermistor problem, all do not find a kind of easy method both at home and abroad.
Purpose of the present invention: the present invention has overcome the shortcoming of the non-linear and inconsistency of thermistor, make and to make temperature-sensing element and the thermometer made has enlarged temperature-measuring range and improved temperature measurement accuracy by thermistor, and can replace the thermistor of different parameters easily, can also be used for remote temperature measurement and temperature control.
Technical characterictic of the present invention is: the first, and employing voltage one frequency-conversion circuit has been realized the intrinsic match family curve T with thermistor
-1=A+Blog R
tBe transformed into frequency-temperature F(HZ)=F
0+ B
1The linear function of T, thus overcome the non-linear shortcoming of thermistor.The negative pulse width τ of the voltage controlled oscillator in second regulation voltage, one frequency-conversion circuit
pFactor τ with the decision positive pulse width
d, the different thermistor of alternative parameter has overcome the difficulty that the thermistor inconsistency is brought to replacement simply.The 3rd, adopt self-balancing bridge to convert dut temperature to magnitude of voltage, and eliminated and connect the influence that transmission line produced of thermistor, thereby can accurately measure in tens kilometers the temperature of any arbitrarily.The 4th, adopt simple, reliable decade count display circuit, can show positive and negative temperature value simultaneously.
Detailed content of the present invention: figure (1) is the embodiments of the invention block schemes, as temperature-sensing probe, form voltage one frequency-conversion circuit by the thermistor that places the dut temperature zone (1) through self-balancing bridge (2), differential amplifier (3), logarithmic amplifier (4), to voltage controlled oscillator (5); All the other form temperature display unit, and it comprises: by control circuit (7), counter (17), with door (13) and (14), a trigger (18), latch/decipher/driver (21) and LCD (24) is formed the decade count display circuit; Form the sign symbol display circuit by latch (19), XOR gate (20); Driving radix point by not gate (22) shows.
Figure (2) is the circuit diagram of self-balancing bridge (2).Transistor Q among the figure
1And voltage stabilizing diode D
1And resistance R
1, R
2Form constant-current source circuit, a steady current I is provided for following electric bridge
SOperational amplifier (25), resistance R
3, R
4And capacitor C
1, C
2And diode D
2Constitute integrator, its output controlling filed effect transistor Q
2, be used for keeping electric bridge A point and B point current potential and equate.Because R
3And R
4Resistance equates, so the electric current that flows through in each brachium pontis is 0.5I
SR
5During for remote temperature measurement, connect the transmission line resistance of thermistor, with the resistance value R of an arm in the balancing circuitry
6Equal R
5Like this, work as R
tWhen changing along with dut temperature, Q
2Drain electrode and voltage between source electrodes follow R all the time
tChange, and, detect R through differential amplifier (3) by B, the output of C two ends
tThe actual voltage value at two ends.Again through logarithmic amplifier (4) input voltage controlled oscillator (5).
Figure (3) is the circuit diagram of voltage controlled oscillator (5).By operational amplifier (26), 555 timers (27), field effect transistor Q
3, voltage stabilizing diode D
3, resistance R
7-11And capacitor C
3-4Form.The negative pulse width τ of its output
pWith positive pulse width τ
oBe respectively:
τ
p≈0.7R
9C
4（1）
τ
o＝τ
d/｜V
1｜ （2）
Wherein
τ
d≈V
cR
7C
3（3）
V in the following formula
cBe voltage stabilizing diode D
3The voltage of setting up.According to the transport property and the mathematical derivation of circuit, at τ
pAnd τ
dWhen satisfying following the relation respectively
τ
d＝-A
oτ
p（4）
B
1＝A
o/B
oτ
p（5）
The output frequency F and the dut temperature T of voltage controlled oscillator are linear, promptly
F＝F
o+B
1T （6）
In (4) and (5), A
oAnd B
oIt is the main constant that characteristic determined by thermistor.In (6), F
oBe constant, B
1Be the variable quantity of dut temperature its output frequency when changing 1 ℃, T represents with Celsius temperature.Its actual measured results is shown in figure (6).
Simultaneously, for a certain thermometer that designs by (4) and (5) requirement, in the time will replacing the thermistor of different parameters, as long as two trimmers in the regulating circuit, promptly regulate τ
pAnd τ
dStill in the time of satisfying (6) formula, with the parameter F of original design
0And B
1Value identical.So just can under the condition that does not influence temperature measurement accuracy, replace thermistor.
In order to show dut temperature multi-functionally, its display unit comprises: decade count shows, sign symbol shows and the radix point displacement shows, wherein, in the decade display circuit, selects B
1=-10HZ/ ℃ or B
1=-100HZ/ ℃.We select B now
1=-100HZ/ ℃ then (6) just can become
F＝F
o-100T
We can determine that by frequency dut temperature value T is simply according to following formula
T＝（F
o-F）/100 （7）
That the display circuit of figure in (1) designs by the requirement of (7) exactly, wherein control circuit (7) produces five pulse signals, they are respectively zero clearing (8), put number (9), sampling (100) is sent and is counted (12), 32HZ symmetrical square wave (11).(17) be to preset BCD up-down counter (doubleclocking).(15), (16) be respectively the addition and the subtraction counting input end of counter (17), not gate (22) drives that radix point that liquid crystal (24) shows realized will (6) middle F
oThe result of-F is by 100 functions of removing.
Display circuit is realized F
oThe function of-F is to finish under the domination of control circuit (7).At first quenching pulse (8) is trigger (18) zero clearing, then closes with door (14), (13) open.Put rapid pulse then and dash (9) constant F
oInsert (17), when sampling pulse one arrives, frequency is that the pulse signal of F is through entering (17) counting that subtracts with door (13).If F＜F
oThe time because borrow pulse do not appear in counter (17d), so trigger (18) maintain the original state, under the effect of sending rapid pulse to dash (12), counter (17
A-d) data parallel send into (21) feed flow crystalline substance (24) and show, send the content of trigger (18) (19) to show "+" symbol simultaneously through XOR gate (20) feed flow crystalline substance (24), expression demonstration this moment be positive temperature value; If F＞F
oThe time, a borrow pulse can appear in counter (17d), makes trigger (18) change original state, closes with door (13) this moment, (14) open, and counter (17) changes plus coujnt into, that is to say, at F＞F
oThe time, counter (17) is made plus coujnt after subtracting earlier and counting, and under the effect of sending rapid pulse to dash (12), liquid crystal (24) shows "-" symbol and temperature value, and the expression measured temperature is a negative temperature.The 32HZ symmetrical square wave (23) of (21) output links with the public electrode of LCD (24) among the figure (1).
Effect of the present invention: the digital temperature meter of being invented is that the reading of 0.01 ℃ standard mercury thermometer is made the standard temperature value with scale division value in Water Tank with Temp.-controlled; Measure the output voltage of differential amplifier (3) and logarithmic amplifier (4) respectively with digital voltmeter, measure the output frequency of voltage controlled oscillator (5) with the PB-2 frequency meter.Measurement data is retouched into curve must scheme (4), figure (5) and figure (6).Figure (4) expression R
tThe voltage at two ends is nonlinear with variation of temperature trend; Figure (5) expression is R
tThe value after the voltage at two ends is taken the logarithm and the relation of temperature T remain curve form; The frequency of figure (6) expression voltage controlled oscillator (5) output is linear with variation of temperature.
A remarkable advantage of the present invention is the wide and precision height of temperature-measuring range. In-20～+ 100 ℃ of these the most frequently used temperature ranges temperature measurement accuracy be not more than ± 0.05 ℃. Resolution ratio be 0.01 ℃ can be in ± 99.99 ℃ of scopes thermometric; When resolution ratio is 0.1 ℃, can show that maximum temperature values is ± 999.9 ℃, but because the inherent characteristic of thermistor has limited temperature-measuring range, generally can be in 700 ℃ of scopes thermometric.
Another obvious advantage of the present invention is: thermistor RtTransmission line resistance can in self-balancing bridge, be eliminated, so just can prolong according to actual needs or shorten and connect RtLead, can measure temperature nearby, also can to away from the observer certain the some temperature measure or control.
In addition, utilize the design concept of this digital temperature meter, add the temperature-control circuit of adaptation, just can make the thermometer and the temperature controller that are suitable for using in the different field.
Claims (8)
1, the digital temperature meter of the non-linear temperature-sensitive resistance making of a kind of usefulness, it comprises a temperature-sensing probe of being made by thermistor, the invention is characterized in: also comprise by self-balancing bridge, differential amplifier voltage-frequency translation circuit that logarithmic amplifier and voltage controlled oscillator are formed and the display unit of forming by counter, display circuit.
2, according to claim 1 described thermometer, wherein the voltage controlled oscillator in the voltage-frequency translation circuit comprises: operational amplifier, 555 timers, when the negative pulse of output and positive pulse width when proportional, its transmission feature finally makes frequency and the linear transformation relation of temperature.
3, according to claim 2 described thermometers, wherein, the voltage controlled oscillator in the voltage-frequency translation circuit, two trimmers make f in the regulating circuit
0And B
1Be worth when identical the thermistor of transposing different parameters that can be easy with former design parameter.
4, according to claim 1 described thermometer, wherein, the self-balancing bridge in the voltage-frequency translation circuit comprises constant-current circuit and integrating circuit, and makes the resistance value R of an arm in the balanced bridge
6With transmission line resistance value R
5Equate,, carry out remote temperature measurement so that offset the influence of transmission line.
5, according to claim 1 to 4 described thermometer, wherein, display unit comprises decade count display circuit, sign symbol display circuit and radix point displacement display circuit.
6, according to claim 5 described display units, wherein, the decade count display circuit comprises: control circuit, counter, with door, latch/decipher/driver, trigger and LCD.
7, according to claim 5 described display units, wherein, the positive and negative display circuit comprises: latch, XOR gate and LCD.
8, according to claim 6,7 described display units, wherein, radix point displacement display circuit comprises not gate, drives liquid crystal display.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 85105275 CN85105275A (en) | 1985-07-05 | 1985-07-05 | Digital temperature meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 85105275 CN85105275A (en) | 1985-07-05 | 1985-07-05 | Digital temperature meter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN85105275A true CN85105275A (en) | 1986-12-31 |
Family
ID=4794376
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 85105275 Pending CN85105275A (en) | 1985-07-05 | 1985-07-05 | Digital temperature meter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN85105275A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101782439B (en) * | 2008-12-31 | 2012-12-05 | 英特尔公司 | Ratio meter for temperature sensor |
| CN104390719A (en) * | 2014-11-21 | 2015-03-04 | 广西智通节能环保科技有限公司 | Temperature measuring system |
-
1985
- 1985-07-05 CN CN 85105275 patent/CN85105275A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101782439B (en) * | 2008-12-31 | 2012-12-05 | 英特尔公司 | Ratio meter for temperature sensor |
| CN104390719A (en) * | 2014-11-21 | 2015-03-04 | 广西智通节能环保科技有限公司 | Temperature measuring system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111595402B (en) | Constant-temperature difference type thermal gas mass flow meter | |
| USH562H (en) | Accurate electronic thermometer | |
| CN85105275A (en) | Digital temperature meter | |
| Hoge | Comparison of circuits for linearizing the temperature indications of thermistors | |
| US3086169A (en) | Systems for measuring electrolytic conductivity | |
| Zeffert et al. | Thermistor Temperature Recorder | |
| JPS6129657B2 (en) | ||
| CN203882485U (en) | Experimental device for designing resistance thermometer by employing non-balanced bridge | |
| US3940686A (en) | Linear output bridge circuit | |
| SU1089432A1 (en) | Device for measuring temperature and temperature difference | |
| SU708174A1 (en) | Temperature difference measuring device | |
| SU773455A1 (en) | Temperature measuring apparatus | |
| JPS60187833A (en) | Temperature detection apparatus | |
| SU1397743A1 (en) | Multipoint digital thermometer | |
| SU1672236A1 (en) | Temperature measuring device | |
| SU1506297A1 (en) | Device for measuring temperature | |
| US3512394A (en) | Temperature and composition dependent property measuring | |
| SU892234A1 (en) | Temperature to digital code converter | |
| SU864091A2 (en) | Conductometer | |
| SU271428A1 (en) | THERMISTOR THERMAL SENSITIVE DEVICE | |
| JPH0461288B2 (en) | ||
| SU1530995A1 (en) | Thermoanemometric device for with automatic temperature self-compensation | |
| SU263211A1 (en) | DEVICE FOR MEASURING DIFFERENCE TEMPERATURES | |
| US3177719A (en) | Means for indicating small changes in a physical or chemical condition | |
| US3495169A (en) | Modified kelvin bridge with yoke circuit resistance for residual resistance compensation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C06 | Publication | ||
| PB01 | Publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |