UL 1434 Asia Thermistor Testing Center launched in Taipei

	Issue 18 (Summer, 2006)

UL 1434 Asia Thermistor Testing Center
launched in Taipei

In April 2006, UL unveiled the Asia Thermistor Testing Center in Taipei, Taiwan. This center specializes in the safety testing and certification of thermistor-type devices according to UL 1434. As Asia is the production base of more than 95% of thermistor manufacturers in the world, the new testing center aims at providing Asian thermistor manufacturers with high-quality safety testing and certification services with shorter project turnaround time. Supported by a group of qualified engineers and technicians as well as customer service representatives, the new testing center can test thermistor-type devices according to special needs of clients and specific national and international requirements.

Advanced testing facilities for thermistor-type devices

The UL Asia Thermistor Testing Center is capable of testing all thermistor-type devices constructed of ceramic or polymeric semiconductor material covered under the standard UL 1434. The new testing center, coupled with the advanced facilities of UL’s existing PWB & Plastic Testing Center in Taipei, which include forced air-exchanged oven, humidity chamber, and freezer, is able to support manufacturers with comprehensive testing services according to UL 1434.

Equipment	Rating	Capacity	Remarks
R/T System, Oven Type	20~250°C/±1°C 10µO~1GO	160	Automatic
R/T System, Oil Bath	20~250°C/±0.002°C 0.1µO~110MO	40	Automatic
Time To Trip Calibration Tester	5µs~50s/div	-	Proposed complete automation measurement on Quarter 1, 2007
DC Aging Testers / Hold Current Calibration Tester	0~60V/0~3A	6*24	Total 24 sets, available for series/ parallel to get 120Vdc/6 A
DC Cycling Testers	0~16V/0~185A, 0~32V/0~95A, 0~60V/0~50A, 0~150V/0~20A	72 722 722 72	Automatic, each unit with 72 channels and separated into 4 groups and each group can adjust voltage and current independently, forced cooling rack
AC Cycling Tester	0~300V/0~20A, 0~600V/0~5A	27*5 27	Pre-wired, each unit with 27 channels and separated into 9 groups and each group can adjust voltage and current independently, forced cooling system, automatic
Thermal Cycling Tester	-65~0°C/40~300°C	24	Automatic
Note: Capacity means the maximum number of samples an equipment can handle at each time.

Table 1: UL Asia Thermistor Testing Center's main testing equipment

R/T (Resistance/ Temperature) testing equipment

R/T testing is a critical process of thermistor-type devices certification service. It is a major factor determining the queue time of the testing process. The Thermistor Testing Center features the installation of computerized-controlled equipment that operates on a round-the-clock basis. While traditional manual testing always incurs a bottleneck due to the constraints of manpower and equipment capacity, the new facilities can effectively shorten the testing queue time. The Thermistor Testing Center is equipped with the latest programmable oven-typed R/T systems and oil-bath R/T systems. Besides, it uses the advanced digital multi-meter (DMM) measuring equipment, AGILENT 3458A and HIOKI 3541, which operate in the AGILENT VEE Pro graphical programming environment on the reliable IEEE-488 platform.

Overload, endurance, and cold operational cycling testing equipment

With high variability of product samples, traditionally Overload, Endurance, and Cold Operational Cycling Testing is conducted by means of manual wiring. Manual wiring requires the technicians of the testing laboratory to spend a lot of time on assembling the testing equipment and test circuit, which however have to be disintegrated after the testing process. In order to eliminate the hassles of manual wiring, UL has devised a Cycling testing system that can flexibly accommodate the designs and structures of different models of thermistors. With built-in electric circuits, the new Cycling testing system help technicians to streamline the testing process of thermistors. To configure the testing environment, the technician now just need to clamp the product sample to the test jig, and then preset the electric voltage, current, number of cycle, and the duration of on time/ off time. The new Cycling testing system therefore significantly shortens the turnaround time of testing thermistor-type devices.

Cold thermal cycling tester

The popularity of digitalized products has fostered the development of sensing-type thermistors on the market. Starting February 15, 2006, according to UL's Significant Interpretation, polymeric based current limiters can conduct thermal shock cycling test for meeting manufacturers' I-hold specifications during the certification process. To cater to the specific testing needs of sensing-type thermistors and polymeric based current limiters, the Thermistor Testing Center features the installation of oil-bath R/T testing system as well as Cold Thermal Cycling Tester. By using pneumatic operated mechanism, the advanced Cold Thermal Cycling tester can create ambient temperature changes for cold thermal cycling operation in an efficient and energy-saving manner.

Obtaining certification for thermistor-type devices

To apply for certification for your thermistor-type devices, contact UL’s customer service representatives nearest to your region. Upon receiving your inquiries, UL will get touch with you for further procedures of document and sample submission, as well as arrangement of construction review and product testing.

To facilitate the application process of thermistor-type certification service, manufacturers can refer to Table 31.1, UL 1434 and declare the characteristics in terms of electrical specifications, operating temperatures, product model number and other details.

For the purpose of determining test conditions, a manufacturer shall declare values for each of the characteristics indicated by an “X” in the following table for the respective thermistor type (From Table 31.1, UL 1434)

Characteristic	Thermistor Type
	PTC					NTC

Beta value (B)	-	-	-	-	-	X^B	X^B
Calibration class number (C1, C2, C3 or 4)	R	R	R	R	R	R	X
Capacitance-load, or Joule rating	-	-	-	-	-	-	R
Current-functioning (Ifun ) or trip (It )	-	-	R	-	-	-	-
Current-inrush current (I-inrush)	R	-	-	-	-	-	R
Current-hold (Ih )	-	-	R	-	-	-	-
Current maximum (Imax )	-	R	R	-	R	-	R
Current-short-circuit (Isc ) maximum	-	X	X	-	X	-	-
Current-steady-state (Iss )	R	R	X	-	R	-	R
Coil impedance	-	-	-	-	R	-	-
Resistance-R25 and tolerance	R	R	R	R	R	R	R
Temperature-maximum operating ambient	-	R	R	R	X	R	X
Temperature-switching (Tsw ) or trip (Ttr )	R	R	X	R	R	-	-
Temperature-maximum surface (Ts )	R	R	R	-	R	-	R
Time-to-Trip	-	-	R	-	-	-	-
Voltage-insulation rating	X^C	X^C	X^C	R^C	X^C	R^C	X^C
Voltage-maximum (Vmax )	R	R	X	-	R	-	-
Voltage-rated (Vr )	R	R	R	-	R	-	R
Notes The "R" designation indicates ratings for the device that are required to be provided by the manufacturer. The "X" designation indicates characteristics of the device that the manufacturer shall declare and is verified by testing. The range of operating ambient temperature shall be specified. A beta value (B) is not required. For devices declared by the manufacturer as insulated.