YSI 700 Temperature - Resistance Values

Have you tried asking Yellow Springs Instruments?

Re: YSI 700 Temperature - Resistance Values

For 50 years YSI was known for their precision thermistor temperature sensors. I was a serious customer, buying many thousands of their 0.1ºC interchangeable sensors for use in Sea Data Corporation products in the 1970s and 80s (I've long preferred thermistor sensors over thermocouple sensors for 0.025ºC to 0.2ºC precision measurements). All the YSI sensors we purchased came wrapped with a page of tiny print detailing the sensor's performance and including a table of resistance vs temperature.

According to the company's history page, "Many changes have come about since the start of the new millenium. Rick Omlor became YSI's third President/CEO in 2002. In 2005, Rick and his leadership team made the strategic decision to focus the business in a select few areas rather than following the 60-year history of ever broadened markets and sensor development."

In 2005 the YSI Temperature New Jersey facility was closed. In 2006 the YSI Temperature division was sold to Measurement Specialties, Inc.

The Measurement Specialties thermistor-product web pages don't mention YSI, but they do have the old YSI sensors there, with many of the same part numbers. However, I see that companies like Cole-Parmer still sell the sensors using the YSI name to identify them. Google searches on YSI sensors yields lots of links. Some will get you copies of old YSI documents, such as this useful 85-page 1998 YSI Precision Thermistor and Probes catalog buried in the Advanced Industrial Systems web server, or a 43-page 2001 YSI catalog buried at Measurement Specialties. This company make many types of sensors, and as with YSI, temperature sensors are only a piece of their business. Their website isn't as helpful as it might be, for example the 44018 sensor mentioned below, and thermilinear, bring up not found errors on their internal search.

The YSI 700-series of "reusable" probes encompass a variety of sizes and shapes of protective housings, and when ordering them in the old days you were allowed to specify the specific model of bare encapsulated thermistor that went into the probe. In general you could also specify whether it was a single two-lead thermistor, such as one in the 44000 series, or a "thermilinear" component, which has two or even three thermistors in a network. A single thermistor has a non-linear resistance plot, which can be linearized over a limited temperature range with a shunt resistor. If you add more thermistors and resistors you can extend the linearized range.

The 1998 YSI catalog mentions black three-pin plug connectors for the 700 series probes, which implies the simple two-thermistor "thermilinear" component. You generally get two special ¼-watt 0.1% precision resistors with it, which must be hooked up externally to complete the sensor. The situation is further complicated because you can use different sets of resistor-pair values to optimize the linearization for different temperature regions.

As an example, the 44018 is a popular 3-lead thermilinear sensor (the picture should show three leads). Its two thermistors have the values of 6.00k and 30.0k at 25ºC. The catalog says four standard networks, i.e., resistor pairs, are available in the -30ºC to +100ºC range to go with the 44018, these are p/n 44301 through 44304. Or you can order a sensor+resistor combination.

For example, for a 44018 plus 44301, that's called a 44201, and they're in stock at Newark for $64.51 each (sorry, the datasheet links are wrong). For the 44301 the two resistors are 3200 and 6250 ohms. These are lower in value than the other three sets, so they're meant to optimize for higher temperatures, 0ºC to +100ºC in this case. The YSI catalog says the combined network resistance is Rt = 2768.23 - 17.115 T, so the resistance would drop from 2751 ohms at 0ºC to 2340 at 25ºC to 1057 ohms at 100ºC.

If you don't have the exact matching resistors, you can order them, or you can use nearby-value parts from your shop's standard 1% inventory.

The Measurement Specialties former "YSI" thermistor division is still located in Dayton, OH, and the phone number is 1-800-747-5367. Even though their website won't serve up new thermilinear datasheets, etc., I called and confirmed that they do in fact manufacture and sell the product. That's good to know. They suggested using the old YSI catalog for design information.

Provide me with the part number and I can give you the datasheet

You can use a resistor "Decade Box" to get what ever temperature readings you need!

It is a box that contain several variable resistance (ohmic) that can be adjusted to from 0 ohm to several Megaohm. There are several to choose from and depending on your requirements you can also pick a decade box with the required accuracy percentage of +/- 1%....

This a common and typical electronic technician's tool used to avoid lengthy computations..