After decades of success, the YSI model 55 Dissolved Oxygen and Temperature Handheld instrument will be discontinued February 2016. This includes item numbers 055200, 055225 & 055250. After February 29th, 2016, we will no longer accept orders for the model 55. YSI will continue to support existing model 55’s for the next 5 years. This is the last of the older-style YSI handhelds to be discontinued.
When looking for a replacement instrument, we suggest the Pro20 or ProODO handheld instrument as suitable replacements. Both instruments are waterproof, rugged and designed for field use with metal, military spec connectors, IP-67 waterproof rating and 1 meter drop testing.
The Pro20 utilizes a membrane covered DO sensor, just like the 55, but uses cap membranes instead of stretch membranes, making it much easier to replace the membrane. Additionally, the Pro20 has a longer warranty, has an internal barometer that allows for a one-touch calibration and has user-replaceable cables and sensors. In addition to connecting a field probe/cable assembly, the Pro20 can also be connected to a lab BOD-style probe.