Laboratory Water Bath

Overview

A laboratory water bath holds a volume of liquid at a stable, set temperature so that samples immersed in it equilibrate to the same value. It is one of the most common pieces of bench equipment: warming reagents and culture media to 37 °C, thawing samples, running enzyme reactions, and holding serological work at controlled temperature. The job is precise temperature control over a large thermal mass, so the design centers on an immersion heater, a stirred stainless tank, an insulated body, and a PID loop that holds the setpoint within a tenth of a degree.

The water itself is the working medium. Its high heat capacity smooths out swings, which is why a bath holds temperature far more steadily than air does, and why even simple units reach ±0.1 °C stability once they settle.

How it works

The bath liquid sits in the Stainless Inner Tank, a drawn stainless reservoir nested inside the outer housing with the Insulation Blanket blanket filling the gap. Insulation does two jobs: it cuts the standby power needed to hold temperature, and it keeps the outer skin cool enough to touch.

Heat comes from the Heating System system. A tubular immersion element lies along the tank floor and transfers its power directly into the liquid. Two independent safety devices guard against boil-dry: a one-shot thermal fuse and an adjustable over-temperature cutout that cut heater power before the empty tank can overheat.

The temperature is measured by the PT100 Temperature Probe, a PT100 platinum probe immersed in the bath. Its reading feeds the PID Control Board, which runs the PID loop and switches the heater through a solid-state relay. PID control trims the duty cycle as the bath approaches setpoint so it eases in without overshooting, then holds steady against heat lost to the room and to cold samples dropped in.

Even heating is not enough on its own, because a heater warms the water around it faster than the far corners. The Circulation Pump pump turns a small impeller that stirs the tank, so the whole volume reads the same temperature rather than stratifying warm-on-top. Samples load on the Sample Rack & Tray, which keeps tubes and flasks suspended in the moving liquid and off the hot tank floor. The operator sets the target and reads the actual value on the Display & Keypad, and the hinged gable lid sheds condensate back into the tank to cut evaporation and protect the setpoint over long runs.