Temperature compensated adapter for a DMM

• US 6,068,400 A
• Filed: 02/27/1998
• Issued: 05/30/2000
• Est. Priority Date: 02/27/1998
• Status: Expired due to Fees

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Nelson, Theodore G., Baker, Clifford E.
• Primary Examiner(s): Bennett, G. Bradley
• Assistant Examiner(s): VERBITSKY, GAIL KAPLAN
• Application Number:
  US09/032,637
• Time in Patent Office: 823 Days
• Field of Search: 374/179, 374/181, 374/208, 439/329
• US Class Current: 374/179
• CPC Class Codes: G01K 7/12 Arrangements with respect to the cold junction, e.g. preventing influence of temperature of surrounding air

Abstract

An adapter suitable for use with a handheld multimeter and a thermocouple probe contains a temperature sensor and input connectors suitable for mating with standard thermocouple probes. Both of these are closely coupled thermally to an isothermal domain. Plugs suitable for mating with the input jacks of a handheld multimeter are disposed within the adapter on the other side of a high thermal resistance zone. Conductors connect these outputs to the input connectors and to the leads of the temperature sensor. A four output version of the adapter is shown for use with a three lead temperature sensor, and a three output version is shown for use with a two lead temperature sensor. The output plugs can paired to be more compact and easier to use through the use of dual-signal single-axis banana plugs.

Claims

1. An adapter for use in making thermocouple based temperature measurements using a handheld multimeter and a thermocouple probe, the multimeter having three or more signal input connectors, and the thermocouple probe having first and second voltage output connectors, with a voltage difference between the first and second voltage output connectors being representative of a temperature difference between a measurement thermocouple junction and a reference thermocouple junction, the reference thermocouple junction being located near and being closely thermally coupled with the first and second voltage output terminals, the adapter comprising:

an isothermal material defining an isothermal domain within a first portion of the adapter;

a first signal input connector for connecting the adapter to the first voltage output terminal of the thermocouple probe, the first signal input connector being closely thermally coupled to the isothermal domain;

a second signal input connector for connecting the adapter to the first voltage output terminal of the thermocouple probe, the second signal input connector being closely thermally coupled to the isothermal domain;

a temperature sensor, the temperature sensor being closely thermally coupled to the isothermal domain, and having a power supply input, a common connection, and producing a temperature output voltage signal at a temperature signal output, the level of the temperature output voltage signal being indicative of the temperature sensed by the temperature sensor;

a thermal resistance material defining a thermal resistance zone within a second portion of the adapter;

a first signal output connector for connecting the adapter to a first terminal of the handheld multimeter, the first signal output connector being electrically coupled to the first signal input connector and thermally isolated from the isothermal domain by the thermal resistance zone;

a second signal output connector for connecting the adapter to a second terminal of the handheld multimeter, the second signal output connector being electrically coupled to the second signal input connector and the common connection of the temperature sensor and being thermally isolated from the isothermal domain by the thermal resistance zone; and

a third signal output connector for connecting the adapter to a third terminal of the handheld multimeter, the third signal output connector being electrically coupled to the temperature output for conveying the temperature output voltage signal and being thermally isolated from the isothermal domain by the thermal resistance zone.

2. An adapter according to claim 1 further comprising a fourth signal output connector for connecting the adapter to a fourth terminal of the handheld multimeter, with the fourth signal output connector being electrically coupled to the power supply input of the temperature sensor.

3. An adapter according to claim 2 wherein the first and second signal output connectors are both part of a same dual-signal single-axis plug.

4. An adapter according to claim 3 wherein the same dual-signal single-axis plug is a "banana"-type plug.

5. An adapter according to claim 4 wherein the third and fourth signal output connectors are both part of a same dual-signal single axis plug.

6. An adapter according to claim 5 wherein the same dual-signal single-axis plug is a "banana"-type plug.

7. An adapter according to claim 1 wherein the first and second signal output connectors are both part of a same dual-signal single-axis plug.

8. An adapter according to claim 7 wherein the same dual-signal single-axis plug is a "banana"-type plug.

9. An adapter according to claim 8 wherein the third and fourth signal output connectors are both part of a same dual-signal single axis plug.

10. An adapter according to claim 9 wherein the same dual-signal single-axis plug is a "banana"-type plug.

11. An adapter according to claim 1 wherein the third signal output connector is also electrically coupled to the power supply input of the thermocouple, and both power and the temperature output voltage signal share the same path through the third signal output connector.

12. A combination of an adapter and a thermocouple probe for use in making thermocouple based temperature measurements using a handheld multimeter, the multimeter having three or more signal input connectors, and the thermocouple probe having first and second voltage output connectors, with a voltage difference between the first and second voltage output connectors being representative of a temperature difference between a measurement thermocouple junction and a reference thermocouple junction, the reference thermocouple junction being located near and being closely thermally coupled with the first and second voltage output terminals, the combination comprising:

an isothermal material defining an isothermal domain within a first portion of the adapter;

a first signal input being closely thermally coupled to the isothermal domain and permanently connected to the first voltage output terminal of the thermocouple probe;

a second signal input being closely thermally coupled to the isothermal domain and permanently connected to the second voltage output terminal of the thermocouple probe;

a temperature sensor, the temperature sensor being closely thermally coupled to the isothermal domain, and having a power supply input, a common connection, and producing a temperature output voltage signal at a temperature signal output, the level of the temperature output voltage signal being indicative of the temperature sensed by the temperature sensor;

a thermal resistance material defining a thermal resistance zone within a second portion of the adapter;

a first signal output connector for connecting the adapter to a terminal of the handheld multimeter, the first signal output connector being electrically coupled to the first signal input connector and thermally isolated from the isothermal domain by the thermal resistance zone;

a second signal output connector for connecting the adapter to the handheld multimeter, the second signal output connector being electrically coupled to the second signal input connector and the common connection of the temperature sensor and being thermally isolated from the isothermal domain by the thermal resistance zone; and

a third signal output connector for connecting the adapter to the handheld multimeter the third signal output connector being electrically coupled to the temperature output for conveying the temperature output voltage signal and being thermally isolated from the isothermal domain by the thermal resistance zone.

13. The combination according to claim 12 further comprising a fourth signal output connector for connecting the adapter to the handheld multimeter, with the fourth signal output connector being electrically coupled to the power supply input of the temperature sensor.