温度控制方面的一些常见问题和解答

6. JULABO high end products feature the VFD COMFORT-DISPLAY.
This display aims at providing even more illuminating power, clearness and brilliance as well as an even easier operator assistance. It features the unique simultaneous indication of three temperature values: Internal actual temperature, setpoint temperature and external actual temperature are permanently displayed. Furthermore the selected pump stage is visible at all times on the integrated illuminated pump stage display.


7. Which JULABO units feature interactive operator assistance?
JULABO circulators of the 'HighTech' Series, the high dynamic temperature systems 'Presto' and 'Forte HT' as well as LC6 programmable controller feature additionally a 4-line backlit and interactive LCD DIALOG-DISPLAY for user-friendly operation. Besides actual and setpoint values it is possible to indicate, for example, the control mode (internal/external), heating or cooling capacity as well as external setpoint values.


8. What is the difference between PID and ICC temperature control?
JULABO PID1, PID2 and PID3 controllers have fixed control parameters (Xp, Tn, Tv). These can be changed manually in PID2 and PID3 controllers in order to get an improved temperature stability especially in external operating mode.

ICC (Intelligent Cascade Control) currently represents the world’s most advanced and absolutely unique temperature control system. ICC features perfect temperature control through automatic and self-optimizing adjustment of PID control parameters according to the application.

ICC temperature control is featured in JULABO circulators of the ‘HighTech‘ series, high dynamic temperature control systems and the LC6 programm-able controller.


9. What benefits do the ‘TCF‘ Temperature Control Features offer?
a) Band limit: When working in external control mode this function allows the user to limit the difference between internal and external temperature to freely selectable values. Advantage: Protection of the temperature controlled equipment through careful temperature application, protection of e.g. glass reactors from thermal shock.

b) Dynamics: Option to choose between aperiodic and normal PID behavior when using internal control mode:

Aperiodic (default value): Perfect, but takes slightly longer to reach the setpoint without overshoots.

Normal: Reaches the setpoint fast, but with small overshoots. The same applies to refrigerated circulators (undershoots).

c) Limit settings: The limits ‘IntMax‘ and ‘IntMin‘ are applicable when operating in external control mode. Fixed temperature limits (maximum and minimum values) can be set for the internal bath temperature. These limits cannot be exceeded by the controller.

d) Co-speed factor: this parameter influences the time for reaching the setpoint temperature when working in external control mode. Increasing the Co-speed factor reduces the time for reaching the setpoint, but the possibility of overshoots increases.


10. What tasks are done by JULABO pumps?
JULABO uses immersion pumps which are designed to work free from mechanical and thermal wear over extended time periods. The main task, beside the internal circulation of the bath fluid, is to constantly supply objects or systems with bath fluid in a closed or open loop. The units of the ‘Economy‘ and ‘TopTech‘ series, as well as JULABO recirculating coolers, feature pressure pumps of different capacities for closed external systems (loop circuits).

The models MC, ME and ‘Presto‘ feature electronically adjustable pump capacities in stages.

All circulators of the ‘HighTech‘ series feature pressure and suction pumps which can also be adjusted electronically in stages. These pump systems can achieve remarkable pressure, suction and flow rate capacities in closed or open external systems.

When working with connected external glass equipment (autoclaves, reactors) the advantage is that by adjusting maximum pressure, damage to the glass vessel can be avoided.

11. What has to be considered when using RS232 interfaces?
It is important to use a null-modem cable to enable communication between the PC and the JULABO unit. RS232 interface cable and USB interface adapter cable are available as accessories.


12. Which refrigerants are used by JULABO?
For more than 10 years JULABO refrigerating systems have been filled exclusively with CFC-free refrigerants.


13. What is the meaning of ‘ACC‘ Active Cooling Control?
The ‘ACC‘ range is the working temperature range in which the refrigeration system remains active as long as refrigeration is desired or required. All JULABO units feature working temperature ranges which correspond to the ‘ACC‘ ranges. Thus the refrigeration system can also be used at high temperatures (e.g. +200 °C) for fast cool-down.


14. What does proportional cooling control mean?
Refrigerated units without proportional cooling have refrigeration systems which are either switched on or off. This means they are either working with 100 % or 0 % cooling power. Systems with proportional cooling have a special electronic valve which can automatically control cooling capacity between 0 % and 100 %. This allows for accurate control of required cooling power at any temperature and at the same time saves energy.


15. Which advantages are featured by JULABO early warning systems (patented)?
The reason for an untimely cut-off caused by the low liquid level protection is a lack of bath fluid. Usually processes involving temperature application should not be interrupted in order to avoid major damages (e.g. when incubating in the circulator bath or when applying temperature control externally to a reactor).

The early warning system for low liquid level indicates through an intermittent signal tone that bath fluid has to be refilled.

Furthermore an undesired change of the set actual value, e.g. through an exothermic reaction, can be detected and indicated acoustically. For this purpose limit settings, e.g. 2 °C above and below the actual temperature are set via the display. When there is a warning counter-active measures can be taken.

16. Why can temperature alarm indications be set to automated cut-off?
This is required for special applications, but can be switched back to the normal warning function at any time. Changing to cut-off is especially popular in low temperature ranges in order to use this function as a low temperature cut-off with permanent signal tone.


17. Which norms and standards do JULABO units comply with?
Of course all JULABO units are CE certified and comply with the safety requirements. JULABO units comply with the following harmonized norms: EN 1050, EN 292, EN 61010, EN 60204, EN 563, EN 61326.


18. What does the classification according to DIN 12876-1 indicated on the type label mean?
Terms and classifications are specified in DIN 12876 and provide information on the application. JULABO units belong to the following classification:

Class I: (JULABO abbreviation ‘S1‘): Units of this class feature a fixed high temperature or dry-running protection. The units are only suitable for operation with non-flammable bath fluids.

Class III: (JULABO abbreviation ‘S3‘): Units of this class feature adjustable high temperature cut-off and additional low liquid level protection. The units are suitable for operation with flammable bath fluids.


19. What does JULABO offer beyond DIN?

• High temperature cut-off is adjustable in all circulators. It is indicated on a display (MULTI-DISPLAY LED / VFD COMFORT-DISPLAY) and can be accessed at any time.

• If the set high temperature value or an impermissible low liquid level is detected an optical indication appears and an audible signal sounds permanently.

• All JULABO units include a constant monitoring of the difference between safety and working temperature sensor which cuts-off the unit if the difference between these two sensors exceeds 25 K. The cut-off is also effected in case one of the two sensors is defective and has to be replaced. The safety sensor has an additional function as a dry-running protection.

• Furthermore a plausibility control of both sensors through software is always active.


20. What are permissible ambient conditions for JULABO units?
All JULABO units can be operated failure-free at ambient temperatures between +5 and +40 °C (max. +35 °C for ultra-low refrigerated circulators). Optimal ambient conditions are ambient temperature of +20 °C and approximately 50 % relative humidity

21. Which mains voltages and frequences are permissible?
Information on mains voltages and net frequencies required for safe operation can be found on the type label of each unit.


22. What is the warranty time given by JULABO?
Warranty time for proper operation of all units is 12 months. The 1PLUS-Warranty provides the user with a free extension of warranty time to 24 months, limited to a maximum of 10,000 operating hours. The registration for the 1PLUS-Warranty can be done at www.julabo.de!


23. What has to be taken into account when connecting an external system?
1. Tubing between the circulator and the external system has to be kept as short as possible and has to be secured to prevent slipping off.

2. Tubing, connections and external system have to be well insulated.

3. Use of a suitable JULABO bath fluid.

4. The exchange of energy between the circulator and the external system has to be optimized (e.g. by avoiding strictures in the tubing).

5. When using an external temperature sensor it has to be well integrated into the system.


24. Which advantages does metal tubing have?
Flexible JULABO metal tubing can be connected with the circulator and the external system thus avoiding slipping. The integrated insulation avoids loss of performance.


25. Which bath fluids should be used?
For working temperature ranges up to +80 °C JULABO recommends the use of de-ionized water. Distilled water tends to take in composites from components thus causing corrosion.

JULABO THERMAL bath fluids offer extended temperature ranges. They have the advantage of much smaller specific heat capacities. When selecting bath fluids special attention has to be paid to the flash point and fire point.

Especially when it comes to low temperatures the permissible viscosity as stated in the operating manuals may not be exceeded.

Alcohols, e.g. ethanol, only have a limited range of applications due to their extremely low fire point.

26. Are cool-down and heat-up times shorter when using JULABO THERMAL bath fluids instead of water and alcohol?
The required cooling/heating capacity in Watts or Kilowatts is less when using silicon oils (THERMAL). Therefore heat-up and cool-down times are shorter. The reason is that THERMAL bath fluids have smaller specific heat capacities than water and alcohol.


27. How do you calculate the required cooling or heating capacity?
The following formula can be used for a time-dependent calculation:

Q = (m * c* dT) / t

Q = required cooling/heating capacity in kW

m = mass of material in kg

c = specific heat capacity (water = 4.2 / Ethanol = 2.5 / silicon oil = 1.8) dT = required temperature difference in °C

t = desired cool-down / heat-up time in seconds

One has to take into consideration that the total mass m is the sum of the volumes of different sources: e.g. the volume of the circulator, in the tubing, in the reactor’s jacket, in the reactor.

The simple calculation of required cooling/heating capacity as seen above does not take into account differences in weight of the bath fluids or other factors reducing performance.

Loss of performance is caused e.g. by: tubing (length, insulation), jacketed baths/reactors (material, thickness, surface), high ambient temperatures, open applications (surface). To allocate sufficient cooling / heating capacity a safety factor of 20-30 % should be integrated into the calculation.


28. What about the JULABO online remote diagnosis with ‘black box’ function?
The new circulators with RS232 interface feature a special function to support the enduser. During operation a black box which is integrated in the circulator works unnoticed and invisible in the background recording all relevant data of the last 30 minutes. In case of a problem this data can be downloaded via software from the circulator to the PC and sent to JULABO by e-mail. Based on this data fast and efficient support can be provided. The software ‘EasyBlack Box’ is available as a free download at www.julabo.de.


Further topics:

29. Why do some circulators have pumps with just pressure ratings, and others have pumps with pressure and suctions ratings?
Some Julabo circulators (EC, MP, and MD, for example) have a single centrifugal pump. This pump draws fluid from the bath tank and circulates it externally. If no external system is connected, the pump can be adjusted to circulate internally. Other Julabo circulators (MW, HE, HD, HP, SD, SP, TD, and TP, for example) have two centrifugal pumps. One is set up to circulate fluid from the tank externally, while the other is designed to circulate fluid from the external system to the bath tank. In other words, there is a pressure pump and a suction pump. Each pump has its own ratings. When used in combination, the pumps can provide even higher flow rates than using either single pump alone.


30. What is CE approval?
CE stands for "Electromagnetic Compatibility". It is the European safety standard for electronic components, which contains requirements similar to FCC, UL, and CSA standards in North America.

31. What is the difference between temperature accuracy and temperature stability?
Accuracy is simply the deviation between a measured value and the actual value. In the case of Julabo circulators, the accuracy would be the deviation between the displayed bath temperature and the actual bath temperature. Stability is the maximum deviation from a nominal value over time. For Julabo circulators, temperature stability is the maximum deviation from the setpoint once steady state has been reached.


32. At what ambient conditions are Julabo units tested to determine product specifications?
All Julabo units are tested at ambient conditions of 20°C and 50% relative humidity. All catalog specifications are derived from these results.


33. What types of materials are the baths constructed of?
AISI Stainless Steels 304, 304L, 316, and 316L.


34. What is the difference between the Pt100 sensor and thermocouples?
There are several differences. Pt100 sensors are actually RTDs (resistance temperature detectors), which are usually more accurate than thermocouples, but generally have a smaller operating range. Thermocouples are usually cheaper, and measure temperatures as a function of voltage across the union of two dissimilar metals. RTDs are more stable, and measure temperatures as a function of the resistance of a particular metal at the temperature being measured.


35. What is the difference between specific types of thermocouples (J, K, R, S, T)?
All of the thermocouple types function in the same manner. The only real difference is in the construction and the temperature vs. voltage relationships. The construction of the thermocouple involves the use of two dissimilar metals. Depending on which metals are used, temperature ranges and accuracies (as well as cost) can vary greatly.

36. What is full range (or active) cooling? What are its benefits?
Full range cooling simply means that the refrigeration system in a particular unit can and will operate throughout the entire range of temperatures that the circulator is rated for. Many suppliers limit their refrigeration systems to low temperatures only, because their refrigeration components will be damaged if exposed to high temperatures. JULABO systems that feature full range cooling can safely operate at the highest temperature the circulator is rated for. Full range cooling greatly decreases cooling times from high temperatures.


37. What types of RTD's are compatible with JULABO units?
100 Ohm Platinum RTD's, with European Alpha (American Alpha will work, but with degraded results). European Alpha is also referred to as DIN 00385.


38. What should be done to optimize temperature control with my chiller, heater or circulator?
Insulate well, minimize the distance from the Julabo unit to the application, increase the flow by using the maximum diameter tubing, and use an external probe where possible.


39. Why does the circulator go to reset when the compressor of the cooling unit is switched on?
There may be a reduction in the power supply due to an unstable network. This may cause the compressor to draw excess current for a short period. This power reduction results in the unit being supplied with insufficient power supply, thus triggering the reset


40. What protection does the fuse provide in the Unit itself?
The fuse provided in the unit is larger than the consumption of current, required by the Unit. The size of the fuse is shown on the label with the unit. Please note that when the unit is first switched on it can draw extra current for a short while.

41. What considerations are there when choosing bath fluids for a JULABO Unit?
The viscosity of the fluid should not be higher than 30 cSt at the lowest operable temperature. Fluids containing water should also not be used. If fluids with higher viscosity or those containing water are used the lowest possible temperature achievable by the bath will not be reached. Specifications of all JULABO refrigerated baths are determined with the use of a 97% purity Ethanol.


42. If the message ‘Cerr’ occurs when switching on a new Cooling Unit, what can I do?
Check the Control Cable (grey) is connected between the Circulator and Cooling Unit. This cable provides the signal connection between both units. The cable is packed in a separate box.


43. During heating a bath filled with oil, the error message ‘E06’ (sensor alarm) appears, what can be checked?
Check the temperature range of the oil being used. If a different fluid other than supplied by JULABO is being used, check the viscosity of the fluid at ambient temperature. If the viscosity between the range of 20 to 40°C exceeds 30 cSt the pump will be overstressed. Using bath fluids other than those provided by JULABO may invalidate the warranty of the unit.


44. A unit in the TopTech Series (MP, MD, MV or MW) shows the message ‘E06’ which changes to ‘E01’ after a time, what should I do?
Check the fluid is at the correct level in the bath, if too low the low-level liquid adapter will trigger these error messages.


45. The unit is alarming and I have tried resetting the alarm by turning the unit off and on, but the alarm is still indicated, what can I do?
After a reset, wait approximately 5 seconds, whilst the Unit is in the switched off mode then switch back on via the main switch. This should delete the alarm memory.

46. While heating up the bath, by using JULABO Thermal Bath Fluid, for a short while oil bubbles out of the bath.
Often volatile components escape as gas phases of the fluids, when heating up the bath fluid for the first time. This is harmless and only happens once, whilst the bath liquid is being de-gassed.


47. Which Bath Fluid is recommended for my application?
Recommendations are given in the operating manuals for the Unit. The bath desired temperatures determines the type of bath fluid recommended:

Between +5°C and +90°C water can be used
Up to -20°C a water-glycol mixture (ratio 1:1) can be used
When choosing silicone oil, the maximum working temperature must be a minimum of 30°C below the flash point of the fluid. At the minimum working temperature the fluid should have a viscosity greater than 30cSt.


48. What different types of tubing are offered by JULABO?
JULABO offer a variety of different types of tubing to suit applications:

CR (Chloroprene) Tubing (-20° to +120°C) suitable up to max 0.8 bar pressure
Viton Tubing (-50° to 200°C) suitable for maximum 0.8 bar pressure
Triple Insulated Tubing (-100° to +350°C) suitable for maximum 3.8 bar pressure


49. What are the advantages of using a HT Circulator with a C.U. Cooling Unit?
The C U Cooling Unit allows the bath temperature to be cooled down at a very fast rate. The amount of cooling water used in the C.U. Cooling Unit is controlled i.e. cooling water is only supplied as and when required.