Unity Lab Services 3110 Series Temperature Sensor Instructions

3110 Series Temperature Sensor
Information 

3110 Series Temperature Sensor

This document provides basic information about the proper operation and function of the temperature sensor in the 3110 Series CO2 incubator. The sensor description, location, method for testing, and common error types are outlined.

3110 Series CO2 Temperature Sensor

• The control and overtemperature (safety) sensors are thermistors.
• The glass bead thermistor is sealed inside a stainless steel protective sheath.
• These devices have a negative temperature coefficient (NTC). This means that as the measured temperature goes higher, the resistance of the sensor (thermistor) goes lower.
• The full range of the temperature display is 0.0C to +60.0C
• If either sensor fails in an OPEN electrical state, the temperature display will read 0.0C plus any positive offset from previous temperature calibration stored in memory.
• If either sensor fails in a SHORTED electrical state, the temperature display will read +60.0C.

Photo of temperature/overtemperature sensor, part number (290184):

Location:

• Both sensors are inserted into blower scroll in overhead chamber area.

Viewing temperature sensor values:

• Control temp sensor value is displayed in upper display.
• Overtemperature sensor value is displayed in lower display when “Down” arrow key is pressed.

Temperature Related Error Messages

SYS IN OTEMP- Cabinet at or above overtemperature setpoint.
Possible cause:

• Actual chamber temperature is greater than OTEMP setpoint.
• Temp setpoint too close to ambient. Reduce ambient temperature or increase setpoint to at least +5C above ambient.
• Temp setpoint moved to a value lower than cabinet actual. Open door to cool chamber or allow time for temp to stabilize.
• Temp sensor failure.
• Temp control failure.
• Excessive internal heat load. Remove source of additional heat (i.e. shaker, stirrer, etc.)

TSNSR1 or TSNSR2 ERROR- Voltage from control or overtemp sensor circuit out of range.
Possible cause:

• Sensor unplugged.
• Poor electrical connection at temp sensor.
• Open sensor. Replace sensor.
• Shorted sensor. Replace sensor.

TEMP IS LOW- Cabinet temp at or below TEMP LOW TRACKING ALARM.
Possible cause:

• Extended door opening.
• Broken door contact (disables heaters).
• Temp control failure.
• Heater failure.

Actual temperature does not match displayed value.

• Incorrect calibration of temp probe. See below for calibration instructions.
• Defective temp sensor. See testing procedure below.
• Error in reference measuring equipment.
• Internal heat load changed. (i.e. heated sample, shaker or other small accessory running in chamber.)

Temperature Sensor Calibration:

• Place the calibrated instrument in the center of the chamber. The measuring instrument should be in the airflow, not against the shelf.

• Before calibration, allow the cabinet temperature to stabilize.
  o The recommended stabilization time from a cold start-up is 12 hours.
  o The recommended stabilization time for an operating unit is 2 hours.

• Press the MODE key until the CAL indicator is illuminated.

• Press the RIGHT ARROW key until TEMP CAL XX.X appears in the display.

• Press the UP or DOWN arrow to match the display to a calibrated instrument.
  o Note: If unable to change the display in the desired direction it is likely that a maximum offset has already been entered during a previous calibration. Test the sensor per instructions below and replace sensor if necessary.

• Press ENTER to store the calibration into memory.

• Press the MODE key to return to RUN mode.

Testing Temperature Sensors:

• The temperature sensor resistance value can be measured with an ohmmeter at a specific chamber temperature.
• The unit should be disconnected from electrical power.
• Connector J4 should be disconnected from main pcb.
• The measured resistance value can be compared to the chart below.
• The nominal resistance at 25C is 2252 ohms.
• Control sensor (yellow wires) can be tested at main pcb connector J4 pins 7 and 8.
• Overtemp sensor (red wires) can be tested at main pcb connector J4 pins 5 and 6.

Electrical Schematic:

Thermistor Temperature vs Resistance (2252 Ohms at 25C)

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3110 Series CO2 Incubators
Revision Date: October 27, 2014
Temperature Sensor Information

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