1. murat hakan ozturk
  2. équipement de la chaîne du froid
  3. jeudi 3 septembre 2015
Dear Colleagues, Many of the prequalified refrigerators have integrated digital thermometers with digital display outside showing instantaneous temperature readings. During the field visits, I have started to notice considerable number of refrigerators with non-functioning digital display. I am curious if this is a coincidence or commonly observed problem. I would be happy to hear your experiences and suggestions. Thanks, Murat
Andrey Kukharenko Réponse acceptée

Dear colleagues,

Let me add up a short opinion with regard to the discussion of SDD fridges and the use of their built in thermometers. I have been involved in temperature monitoring and handling of temperature sensitive goods, especially pharma, for many years in Russia. I can tell you that the current practices maintain that the SDD monitor cannot be an adequate means of temperature control, since the sensor is located at the rear of the fridge and always shows a somewhat lower temperature than that in the fridge. Moreover, such a built in sensor is not subject to сalibration and verification wether it works accurately or not. It also is not capable of recording temperature (some of them can record min/max temp. but without duration info). Almost for a decade the WHO has been promoting the use of specially designed devices for temperature monitoring such as Fridge-tag electronic recorders. As opposed to ordinary thermometers, Fridge-tag devices make it possible to trace and record temperature fluctuations and excursions over 30 days, which provides an accurate and relevant information on temperature in the fridge. Therefore I would recommend that you should avoid relying on SDD temperature sensors and shift to the reliable temperature monitoring devices such as Fridge-tag or Fridge-tag 2 which are prequalified by the WHO and which are world wide used to monitor temperature sensitive goods.

One more point, for information "VMH-E2-01.1: How to monitor temperatures in the vaccine supply chain" page 14:

"Integrated digital thermometers: The current range of prequalified vaccine refrigerators and freezers are equipped with these devices (see Figure 9). An internal temperature sensor monitors the coldest point in the vaccine storage compartment, and an instantaneous temperature reading is displayed on the unit’s control panel. Solar direct-drive refrigerators typically have a device powered by an integrated photovoltaic cell—these do not work at night or in dim light and may have to be activated by a flashlight."

Source: http://www.who.int/immunization/documents/financing/who_ivb_15.04



murat hakan ozturk Réponse acceptée
Dear Subhajit, Thanks a lot for your reply but please note the below point from WHO Immunization in Practice guideline "the vaccine cold chain" module. Stem thermometers are not recommended for use. For many reasons, integrated thermometers for display are the best choice. "Stem thermometers These devices only provide an instantaneous temperature reading. For this reason, WHO no longer recommends them as the main monitoring device in vaccine refrigerators. However, they remain an essential back-up device because they do not require a battery or other power source. Figure 2.15 shows an example. WHO no longer recommends bi-metallic dial thermometers for any purpose because they lose their calibration over time, especially if they are dropped." Dear Soren, I would be glad if you can elaborate more. Do you know some specific WHO prequalified models which require battery? Dear Steve, thanks a lot for elaborate response. I made sure that the problem was not due to dim light. I guess most common reason is failed thermometers. We observed the problem with SDD types. Before the raising the issue to appropriate levels, I just wanted to make sure that this not only our problem. Best Regards, Murat
prabirkc Réponse acceptée
The digital battery runs out Simple solution is to take out the battery and get a new one from a watch shop. It is a simple button battery Most staff àre unaware of this Prabir
Larry Schlussler Réponse acceptée
If the batteries are the problem they could be eliminated by using the refrigerators power system to power the thermometer. For SDD refrigerators a capacitor could be used to store energy for night time operation.
Steve Réponse acceptée
Dear Murat and Subhajit We also are seeing the same problem with some WHO PQS prequalified solar direct drive (SDD) refrigerators. Most of these SDD's use a solar cell on the thermometer display to power it and when interior light level are low these will not function (shining a torch on them usually brings up the display but this is not acceptable for regular use). We also have had to replace failed thermometers too. Did you see this problem with absorption, ILRs, SDD or solar battery powere d fridges? Can anyone suggest a more reliable product or specification so that WHO PQS might benefit and upgrade the equipment specification requirement for thermometers? Steve McCarney Solar Electric Light Fund
Soren Spanner Réponse acceptée
Many of the digital thermometers require a battery
Subhajit Chakraborty Réponse acceptée
Dear Murut, It's quite natural regarding your findings that considerable number of refrigerators with non-functioning digital display but the point is that you should not record temperature from out sided fitted digital display, you should take temperature reading from the inside installed Alcohol Thermometer ( if not installed take initiative to install in ILR/DF) it will give you correct temperature reading. I am totally agreed with you that considerable number of refrigerators with non-functioning digital display, i have the same experience. Thanking you Subhajit

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