Calibrating the Beckman Coulter J2-21 Centrifuge Refrigeration ?
Is there a procedure to Calibrate the Beckman Coulter J2-21, analog meter type of Centrifuge, not digital Refrigeration system.
Reason is that the centrifuge is cooling approximatly 8 to 9 degrees past its set point. The Freon valve & compressor turn off normaly when the black pointer reaches, or passes the green set point pointer displayed on the front temperature meter. I Verifed this by using a second temperature probe, the Temperature meter reports the correct inside chamber temperature. Alternatly I am not even sure which board located at the back inside is the temperature control board. If someone knows could you help me identify the board, cal procedure for this sympthom I would appreciate it.
Thanks for your response to my question. I failed to mention that I was trying to rectify the cooling behavior of the centrifuge when it is operating in the Hold mode (No rotor inside). My feeling is that the system is not shutting the compressor or coolant off in time to prevent -9 degrees of overshoot. Its normal to experience some temperature over shoot in the Hold mode, but not -9-degrees worth. After a while the inside chamber, or rotor temperature will gradually settle. But in this case it just stays at -9 degrees, if temperature is set to 0-degrees. I pretty much think that the rotors inside temperature after a run will be off in temperature as well. Also I'm not sure if the set point on the Temperature Meter's reed switch is off (if there is one ?), and should be adjusted to halt the refrigeration cycle so that the refrigeration cycle stops a little sooner, or can that be adjusted in a circuit ?
Because the only way to regulate the temperature is to modify the timing of the cooling cycle so that it turns the refrigerant flow, or compressor off a little bit sooner, because my feeling is that it is turning it off late. That’s why I was looking to identify the temperature control board, or refer to a circuit calibration procedure for this symptom.
Wayne, as I previously said, you cannot make assumptions on how the refrigeration system is working from a calibration standpoint WITHOUT it actually performing a test run and doing a dunk test of the liquid in the rotor. Beckman centrifuges had what are called anticipation circuitry built into them that help determine when to shut the compressor off. Combine that with the need of a vacuum within the chamber, a rotor spinning, AND the temperature compensation pot underneath the temperature meter set properly is the ONLY way to determine if the centrifuge refrigeration system is working properly. Sorry to be blunt about this but how or what you think should be happening within the chamber is just wrong without everything running as I said. If you want my help then do the testing as I stated. Otherwise I cannot make any other recommendations.
Also, the is no "reed" switch inside of the temperature meter. It has break beam sensors in it and depending on the version of the meter they can be either incandesant or LED. Either way, if they fail there is really nothing you can do about them.