Objective Heater System Instructions

Before You Begin:

·         Check to make sure there is no visible damage in shipment and save all packing materials.

·         The Controller box should contain; controller, power cord, 2.5mm screwdriver, 2mm Allen driver, 1/8” jack, and 3 pin mini DIN connector.

·         Check the packing list and call your supplier if there are any discrepancies.


The Bioptechs Objective Temperature Control System is comprised of two components.  One part is the electronic controller unit; the other is an adjustable objective heater loop which attaches to high numeric aperture (immersion) microscope objectives.  The objective heater is designed to eliminate the heat-sink effect that is accelerated by the presence of an optical coupling medium; oil, glycerin or water.  These objectives have a retractable central tube which contains the optical elements.  Heat is directly transferred to this tube and sensed by a thermistor which is part of an intelligent feedback control loop.  The heater loop requires a minimum of 5mm longitudinal physical contact with the cylindrical objective surface.  In some cases there may be a decorative collar or sleeve on the objective which must be removed in order to permit adequate surface contact for the heater loop.  If an outer collar or sleeve is present we recommend using Bioptechs Objective Wrench and Pliers for proper removal (Bioptechs Part Number:  021523;  See figure 3 – outer sleeve removed).




Objectives are expensive and delicate.  We recommend following the directions below carefully.  Although great care has been taken to produce a reliable product to control the temperature of your objective, there is always some risk.  BIOPTECHS, INC. assumes no responsibility for use of this or any other objective heater.  The user assumes all liability for any damage that may occur due to the use of this objective heater.

Front Panel of Objective Heater Controller


Figure 1

Control Interface Descriptions:

Numeric Display should be illuminated when the controller is turned on.  If it does not light, check the main power source and the fuse block located in the power input module where the AC power cord plugs in.

Display Selector is the black button adjacent to the display.  It selects the source of the information displayed.  When the controller is turned on, the default condition is to display the setpoint value indicated by the red light adjacent to the word Setpoint.  The button selects one of a sequence of display options.  This button can be pressed at any time and has no effect on the temperature regulation functions of the controller.

Display Lights indicate the source of the value displayed on the numeric display.

Setpoint is adjusted by a potentiometer accessible with the 2.5mm screwdriver provided.  To adjust the setpoint, set the numeric display to Setpoint and adjust the potentiometer to the desired value.  If you need to change the setpoint value during your experiment on a routine basis, there is a remote setpoint jack on the back of the controller.  See Remote Setpoint.

Objective is the location where the calibration of the circuit reading the objective thermistor can be adjusted.

Reference is the location where the calibration of the circuit reading the reference probe can be adjusted.

Reset (Red Button) resets the controller if the alarm sounds.  Note:  If the alarm went off there must have been a reason.  Check the objective before resetting the controller.

Calibrate substitutes precision resistors into the circuit that reads the thermistors so that calibration adjustments can be made to a known value.

Objective connector is a six pin mini DIN connector where objective heater is plugged in.

Back Panel of the Objective Controller


Figure 2

AC Power line input, power switch, voltage selector, and fuses are all incorporated in the AC Power Input Module.  The controller can operate between 90 - 260V 50-60Hz, or a 24V battery can be used as an alternate power supply.  The fuse carrier contains two 0.5A slow blow fuses.  The fuses can be accessed by prying the fuse block out of its socket with a small screwdriver wedged under the small slot in the opening of the AC line receptacle.  When replacing the fuse block, make sure to align the arrow on the outside of the fuse block with the closest voltage value to your supply line voltage:

·         For 90-130 supply line voltage place the fuse block with the arrow pointing to 110-120V.

·         For 180-260 supply line voltage place the fuse block with the arrow pointing to 220-240V.

Temp Out is a voltage output direct from two instrument amplifiers reading the thermistors from channel A and B.

The output from this socket is temperature / 10.  37.0°C = 3.70 Volt DC.

The left pin is channel A, center pin is channel B, and right pin is ground.

Remote Setpoint is an analog input that allows the user to set the controllers setpoint from an external DC source. The sleeve is earth ground.  A DC voltage can be applied to the tip of this jack equal to temperature /10. i.e.:  28.5°C = 2.85 Volt.  When the jack is inserted into the controller it will automatically switch to the jacks value.  When removed it will default to the setting on the front of the controller.  The remote setpoint can be used for programming or cycling operating temperatures.

Controller Operation:

  1. Turn the unit on using the main on-off switch located on the rear panel.  All further adjustments are made on the front panel.  DO NOT plug the objective heater into the Objective Controller at this time.

  2. Turn the display switch to the "OBJECTIVE" position.  The temperature display will read a number between -3.7 and -4.2.  This is normal.  Press the black button labeled "CALIBRATE" and make sure the display reads 25.0°C.  If adjustment is necessary, turn the screw in the hole labeled "OBJECTIVE" with the enclosed screwdriver.  CW = increase, CCW = decrease.

  3. Set the display to the "SETPOINT", then insert the enclosed screwdriver into the hole marked "SETPOINT" and adjust the controller 1.8° less than the desired setpoint to compensate for the thermal characteristics of the objective.

  4. Turn the controller OFF.

  5. Mount the objective heater band onto the objective.  (See figure 3 – assembled objective heater)

  6. Plug the objective heater into the controller. Then turn the controller ON.

  7. IMMEDIATELY set the display knob to the objective position and check that it is indicating a value between ambient and setpoint.  If the temperature value displayed is not realistic, turn the controller off immediately.  (Other values indicate possible damage to the temperature probe).  As a safety feature, when the sensor temperature reaches setpoint minus 0.9°C an internal latch is set.  Then if the temperature of the sensor falls below 0.9°C less than setpoint, an alarm will sound and the heater current will be shut off.  The controller will still be on but the output disabled.  If the red reset button located next to the red LED is pressed it will return the controller to cold startup mode and current will return to the heater band.

  8. Always make sure the sensor is in direct contact with the objective.  When you press the reset button, the controller always enters cold startup mode and ignores out of range conditions.  Therefore, it is important that the objective heater is installed properly.

  9. The objective will come up to temperature in about 5 to 10 minutes.  The controller will maintain a constant temperature relative to the value of the contact probe.

  10. It may be necessary to fine-tune the setpoint adjustment for your particular objective.  The temperature of the upper element of the objective can be monitored with the thermistor sensor (small bead on the end of the fine wire extending from the side of the objective heater assembly known as the reference thermistor) to establish the correct setpoint value.

Heater Installation:  (The heater band should be unplugged from the controller and the controller shut OFF)

  1. With the objective secured in the nosepiece of the microscope hold the heater assembly upright with the loop in a superior position. (See figure 3 – assembled objective heater)

  2. Insert the enclosed 5/64mm or 2mm Allen screwdriver into the hole in the top of the metal enclosure. (See figure 4) Rotate the Allen screwdriver clockwise to allow the loop to expand to fit various objectives.  Please note that it may be necessary to gently withdraw the black heater band from the metal enclosure to relieve the slack in the tensioning mechanism.  DO NOT place tension on the heater band wires.

  3. Place the heater loop over the exposed cylindrical end of the objective closest to the specimen making sure the band is evenly applied to this area and that the temperature sensor is also making direct contact with the objective.

  4. Tighten the heater loop onto the objective by turning the Allen screwdriver counterclockwise until the loop is snug.  Use only enough pressure to cause the heater to conform to the objective diameter and uniformly compress the temperature sensor to the objective.  DO NOT OVER TIGHTEN the loop as damage will occur to the tensioning mechanism.

  5. There is a slight mechanical offset to the temperature sensor to maintain contact that may cause the tension mechanism to rise slightly.  It may be necessary to restrict this movement with an elastic band.

  6. Plug the Objective Heater band into the controller. Then turn the controller ON.  (Refer to step seven above)


Note:  To reduce the possible detrimental effects of temperature cycling, it is recommended that the objective be kept in a warming box when not in use.  We recommend the Boekel Warmer (Bioptechs Part Number:  260700)


    Click Here to view a video of assembly. Objective Heater.mpg  ~10MB   

*** CAUTION ***

Excessive use of immersion oil on an objective is detrimental to both the objective and the heater-band.  Immersion oil should not be allowed to come into contact with the heater-band. If contact occurs the heater-band can be cleaned with a tissue dampened with alcohol.


Figure 3


Figure 4



Objective Heater, Standard 16mm – 28mm Temperature Range Ambient to 500C  6 Watts
Objective Heater, Large 26mm – 35mm Temperature Range Ambient to 500C  6 Watts
Sensor Thermistor Temperature Stability ± 0.10C Typically


©Bioptechs, Inc., 4/19/2001

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