MultiLab Benchtop Instrument Probe Selection Overview

September 14, 2023

Hi. My name is Ben Sutter with YSI Lab Solutions. Today, I'm using my YSI MultiLab to measure some pH. Right now, I'm measuring some tap water, so the type of pH probe that I use is wide open. However, I want to be sure that I'm choosing the correct probe for my specific application. In this video, we will go through some features of pH probes that you'll want to consider for optimizing your pH measurement.

An important thing to consider is will my pH probe be compatible with my instrument? The true-line probes are designed exclusively for use with the MultiLab. Any probe with this connector will retain calibration data directly on the probe itself using our IDS, Intelligent Digital Sensor technology. Conversely, many pH probes are analog, making use of this simple BNC connector. If you want to use the BNC connector with the multi-lab, you will need an adapter. There's also an adapter for an analog DIN connector.

Something else to consider is the fill solution. This internal reference solution is the part of the pH probe that maintains a stable potential within the probe. Many probes are filled with a gel reference, which is simple and reliable for most lab work. If you want more control over your reference solution, you can opt for a refillable probe. You can refresh refillable probes with additional reference solution as needed. In addition, we have the science line of probes, which has a double junction reference. The double junction reference is robust, resistant to backflow effects, and offers a fast response time.

Let's talk about the junction type of the probe. The junction is where the fill solution outflows, maintaining a constant potential within the body of the probe. Whichever junction type your pH probe has, assure that the junction is completely covered by your sample to ensure consistent results. A common junction type is the platinum junction. It's a bundle of fine platinum wires that allow minute amounts of outflow, and it's a great all-purpose junction. Here, we have the 4130 IDS probe that uses this type of junction.

Here's another type of junction, the ground joint. This type of junction allows for a very large amount of outflow and is designed to allow for quick discharging of especially thick or particulate heavy applications. It also performs well on applications that have a low ionic strength. A fiber junction, also known as a pylon junction, is like a wick in an oil lamp. This design is similar to that of other YSI environmental products designed for fieldwork.

Temperature is a key element of pH measurement. The majority of probes on the market today have integrated temperature probes. For those that don't, be sure to have a separate temperature probe available, such as the ScienceLine Temp 135. If you are working with samples that are at a constant temperature, you can also choose to enter that temperature manually on the instrument.

YSI offers even more types of probes than were featured here today. Fortunately, we have a handy probe selection guide and a probe application guide available. This will help you to select the most appropriate probe for your pH measurement application.

There's so much more to learn about pH and how it is measured than could be said in this short video. Fortunately, we have many resources available on our website. Check out the pH handbook for more in-depth information. There are also webinars and other pieces of information that are available at


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