ASC Model TD48 Thermal Demagnetizer

Manufactured in the USA by ASC Scientific

TD-48SC Data Sheet

TD-48SC high-capacity single-chamber thermal specimen demagnetizer for geologic samples

  • 25 TO 800°C RANGE


TD-48 Data Sheet

TD-48 high-capacity dual-chamber thermal specimen demagnetizer

  • 25 TO 800°C RANGE

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ASC Model TD-48

ASC’s Model TD48 Thermal Demagnetizer features a large internal diameter oven and three-row sample boat for heating up to 48 one-inch diameter or one-inch cubic geologic samples in a single batch. The oven and adjacent fan-assisted cooling zone are housed in a three-layer seamless magnetic shield, which permits cooling of one batch while a second batch is heating. The cooling chamber has two additional shields which limit the maximum internal field to less than 10 gammas with the instrument oriented perpendicular to the earth’s field. The oven has three independently controlled zones – a large sample zone and two small trimmer end zones – which minimize temperature gradients across the sample zone while keeping overall oven length to a minimum. The system was designed for long service life by incorporating features into the oven and sample boat that protect the internal oven wall from damage.

Controlled Field Coil

An optional controlled field coil encompassing the entire oven and cooling section is available. The coil is wound on a non-magnetic form fitted just inside the inner of the three full-length shields. This coil will produce an axial field of approximately 1 Gauss per ampere of applied current, with a maximum field of 10 Gauss.

Controlled Atmosphere Chamber

An optional controlled atmosphere chamber, for evacuating or introducing a flow of inert gas to surround the samples, is available.


Absolute Temp. Accuracy: 10°C
Temp. Repeatability: 1°C
Max. Temp. Gradient: 10°C Total Over 16″ Sample Region of Oven Chamber with Full Sample Load. 
3°C Attainable with Partial Sample Load
DC Field in Heating Chamber: Less than 50 nT (Gammas), When system is Oriented in East-West Direction
DC Field in Cooling Chamber: Less Than 10 nT (Gammas), 2-5 nT Typical
Heating Time: 48 Specimens From 25°C to 600°C in 45 Minutes
Cooling Time: 48 Specimens From 600°C to 40°C in 25 Minutes
Power Requirements: 115 VAC, 30 AMPS
Size: Oven Unit – 72″ (183 cm) L x 16″ (40.5 cm) W x 13″ (33 cm) H
Control Unit – 17″ (43 cm) W x 15″ (38 cm) D x 7″ (18 cm) H

ASC Model TD-48SC

The TD48-SC thermal demagnetizer has a single chamber in which the samples are heated and cooled. The oven chamber is enclosed in a three-layer, cylindrical mu-metal shield which will attenuate the earth’s field down to less than 10 nT when the system is oriented in an east-west position. Up to 48 samples can be processed in a single batch. The oven has three separate heating zones – a long central sample zone and a short trimmer zone on each end of the central zone. The three heating zones are individually monitored and driven by separate temperature programmers, which are all tied to a single setpoint temperature. This three-zone design ensures that temperature gradients over the length of the sample zone are kept to a minimum. The end zones and the floor of the central zone are lined with a quartz sleeve. This feature minimizes wear to the oven wall, but still allows for excellent feedback between the sample zone thermocouple mounted on the sample boat and the heater windings.

The temperature controllers are microprocessor-based PID type controllers, which are tuned to minimize temperature overshoot during heating and maximize temperature stability at the setpoint. A timer feature allows the user to start a batch of samples and complete the heating and cooling cycles without attending the unit. Heating and cooling times for 48 samples to a temperature of 600 degree C are 45 minutes and 20 minutes, respectively.

Optional features include:
Controlled Field Coil for applying a magnetic field in the oven.
Controlled Atmosphere Chamber for either evacuating or introducing a flow of inert gas to surround the samples.

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