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Unread 07-31-2013, 12:20 PM   #15
NorthernMN
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Join Date: 04-26-13
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Quote:
Originally Posted by QansasjayhawQ View Post
According to Kirchoff's Loop Law, it should work.

There will be an additional drain on any power source as the voltage level generated by the probe will be maintained across both legs of the Y splitter.

There shouldn't be a problem with meat vs. temp probes because the voltage readings are interpreted and processed by algorithms at the end device reading the values, not the probes themselves.

As far as finding one, you should take your probes to Radio Shack and see if you can find a simple splitter or a way to build one.

Good question.
It may not be as easy as finding a splitter that adapts to the two units in question. There are a few different types of thermocouples out there that will produce different voltages at the same temperatures. See this info from wikipedia. Depending on what type of thermocouple the guru and the maverick use you may also need a adapter that changes the voltage output to adapt to the device you are connecting to if they use different thermocouples.

Types[edit]

Certain combinations of alloys have become popular as industry standards. Selection of the combination is driven by cost, availability, convenience, melting point, chemical properties, stability, and output. Different types are best suited for different applications. They are usually selected on the basis of the temperature range and sensitivity needed. Thermocouples with low sensitivities (B, R, and S types) have correspondingly lower resolutions. Other selection criteria include the chemical inertness of the thermocouple material, and whether it is magnetic or not. Standard thermocouple types are listed below with the positive electrode (assuming ) first, followed by the negative electrode.
K[edit]

Type K (chromel {90% nickel and 10% chromium}alumel {95% nickel, 2% manganese, 2% aluminium and 1% silicon}) is the most common general purpose thermocouple with a sensitivity of approximately 41 V/C (chromel positive relative to alumel when the junction temperature is higher than the reference temperature).[9] It is inexpensive, and a wide variety of probes are available in its −200 C to +1350 C / -330 F to +2460 F range. Type K was specified at a time when metallurgy was less advanced than it is today, and consequently characteristics may vary considerably between samples. One of the constituent metals, nickel, is magnetic; a characteristic of thermocouples made with magnetic material is that they undergo a deviation in output when the material reaches its Curie point; this occurs for type K thermocouples at around 350 C . Wire color standard is yellow (+) and red (-).
E[edit]

Type E (chromelconstantan)[6] has a high output (68 V/C) which makes it well suited to cryogenic use. Additionally, it is non-magnetic. Wide range is −50 to 740 C and Narrow range is −110 to 140 C. Wire color standard is purple (+) and red (-).
J[edit]

Type J (ironconstantan) has a more restricted range than type K (−40 to +750 C), but higher sensitivity of about 50 V/C.[2] The Curie point of the iron (770 C)[10] causes an abrupt change in the characteristic, which determines the upper temperature limit. Wire color standard is white (+) and red (-).
N[edit]

Type N (NicrosilNisil) (nickel-chromium-silicon/nickel-silicon) thermocouples are suitable for use between −270 C and 1300 C owing to its stability and oxidation resistance. Sensitivity is about 39 V/C at 900 C, slightly lower compared to type K.
Designed at the [[Defence Science and Technology Organisation\\ (DSTO) of Australia, by Noel A. Burley, type N thermocouples overcome the three principal characteristic types and causes of thermoelectric instability in the standard base-metal thermoelement materials:[11]
  1. A gradual and generally cumulative drift in thermal EMF on long exposure at elevated temperatures. This is observed in all base-metal thermoelement materials and is mainly due to compositional changes caused by oxidation, carburization, or neutron irradiation that can produce transmutation in nuclear reactor environments. In the case of type K thermocouples, manganese and aluminium atoms from the KN (negative) wire migrate to the KP (positive) wire, resulting in a down-scale drift due to chemical contamination. This effect is cumulative and irreversible.
  2. A short-term cyclic change in thermal EMF on heating in the temperature range ca. 250650 C, which occurs in types K, J, T, and E thermocouples. This kind of EMF instability is associated with structural changes such as magnetic short range order in the metallurgical composition.
  3. A time-independent perturbation in thermal EMF in specific temperature ranges. This is due to composition-dependent magnetic transformations that perturb the thermal EMFs in type K thermocouples in the range ca. 25-225 C, and in type J above 730 C.
Nicrosil and Nisil thermocouple alloys show greatly enhanced thermoelectric stability relative to the other standard base-metal thermocouple alloys, because their compositions substantially reduces the thermoelectric instabilities described above. This is achieved primarily by increasing component solute concentrations (chromium and silicon) in a base of nickel above those required to cause a transition from internal to external modes of oxidation, and by selecting solutes (silicon and magnesium) that preferentially oxidize to form a diffusion-barrier, and hence oxidation-inhibiting films.[12]
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