Ta Instruments, Inc.

Waters Investments Limited

Ta Instruments-waters LLC

John W Schaefer

Robert L Danley

Kevin J Reed

John R Reader, Jr

Michael J Levchak

Mark Heyman

Systems and methods for minimizing extraneous forces and calculating corrected weights of samples based on buoyancy factors for a thermogravimetric analyzer (TGA). The TGA includes a balance chamber and a furnace configured to heat a sample. A null balance is provided in the balance chamber and is used to measure the sample weight change during heating. The furnace includes a cylinder open at the top to receive a sample. The bottom of the cylinder is closed except for a small hole that allows a thermocouple to pass through. An infrared heat source may be provided to heat the cylinder. The balance chamber can be thermally isolated from the furnace using an actively cooled plate and a system of heat shields disposed between the furnace and balance chamber. A thermocouple disk is further provided to limit gas flow in the furnace and increase reliability of sample weight measurements.

System and method for a thermogravimetric analyzer having improved dynamic weight baseline

A liquid nitrogen cooling assembly incorporating a liquid detector which feeds back to control the nitrogen supply is disclosed. A pressure-controlled nitrogen source (e.g., a dewar) feeds liquid nitrogen to a heat exchanger mounted to a differential scanning calorimetry (DSC) cell. The DSC cell is cooled as liquid nitrogen in the heat exchanger contacting the cell is vaporized into nitrogen gas. The exhaust (nitrogen gas and, occasionally, nitrogen liquid) is fed to a liquid detection/evaporator assembly. If liquid nitrogen is detected in the exhaust by the liquid detection/evaporator assembly, an indication is fed back using a liquid detection feedback loop to a pressure control device. The pressure control device reduces the amount of pressure on the nitrogen source in order to eliminate liquid in the exhaust. When there is liquid in the exhaust, the liquid detection/evaporator assembly also collects and vaporizes the exhaust liquid so that it can be properly vented to atmosphere in gas form. When liquid is no longer detected in the exhaust, the pressure control device increases the pressure on the liquid nitrogen source until liquid is detected in the exhaust. Subsequent cycles control pressure in this manner to keep the heat exchanger full of liquid nitrogen.

Liquid nitrogen cooling system

An improved differential thermal analysis/differential scanning calorimetry (collectively, DSC) assembly with a furnace block assembly having a measurement chamber and a furnace heater. The measurement chamber has a sensor assembly for receiving a sample material and a reference material. The furnace block assembly is coupled to a generally cylindrical cooling flange through a distributed thermal resistor that allows a constrained heat flow between the furnace assembly and cooling flange. The thermal resistor can also withstand the mechanical stresses associated with the differential expansion and contraction of the furnace assembly and cooling flange without permanent deformation of the thermal resistor. The cooling flange can be coupled to various cooling devices, permitting operation of the overall DSC instrument in a variety of temperature regimes for a variety of applications.

Thermal analysis assembly with distributed resistance and integral flange for mounting various cooling devices

A heat shield and insulation system comprised of multiple layers of metallic sheets separated by small protrusions or dimples in the metallic sheets. The multiple layers are formed by spirally winding a coil of the metallic sheet around the sample enclosure. The protrusions are formed by stamping the metallic sheets, preferably in a random patterns, such that one set of protrusions does not nest in the protrusions formed in a neighboring sheet. The spacing between the layers of metallic sheets is small, such that convection does not occur in the space between the layers. Accordingly, the heat transfer between the layers of the metallic sheets is primarily radiative or via thermal conduction through the gas. The two ends of the helically wound metallic sheet are insulated by multiple thin metallic disks.

Metallic sheet insulation system

A Differential Scanning Calorimeter (DSC) which has constant calorimetric sensitivity over its entire range of operating temperatures from -200.degree. C. to 540.degree. C. The DSC sensor consists of a pair of thin-film Resistance Temperature Detectors (RTDs) which are used to sense the temperature of a sample and the temperature difference between the sample and an inert reference. The RTDs are supplied with an excitation current which varies according to the temperature of the reference to achieve constant calorimetric sensitivity, independent of the operating temperature.

Differential scanning calorimeter

A dynamic and thermal mechanical analyzer incorporating a slide driven vertically in an air bearing guidance system with a large displacement capacity, very low friction and low mass. The position of the slide is measured by digitizing and interpolating two quadrature output signals generated by an optical encoder with very high spatial resolution and a long stroke. A force is applied to the slide using a linear permanent magnet motor with high force, high force linearity and low sensitivity to temperature variations. Position signals derived from the digitized and interpolated quadrature output signals are analyzed as a function of the applied force to calculate viscoelastic properties of a sample of material.

Dynamic and thermal mechanical analyzer having an optical encoder with

The present invention is a thermogravimetric instrument having a ceramic sample support and a ceramic balance beam. The ceramic platform is rigidly attached to the hot end of the ceramic balance beam. An inert metal liner is press fitted into the ceramic sample platform. In a preferred embodiment, a thermocouple is directly attached to the inert metal liner. The thermocouple wires are routed through the length of the ceramic balance beam and are attached to the cold end of the ceramic balance beam with adhesive. The inert metal liner could be fabricated from platinum or from platinum alloys.

Thermogravimetric apparatus

A differential thermal analysis sensor consisting of two low-impedance differential thermopiles. Each thermopile consists of a series of thermocouples joined in series, with the measuring junctions of the thermocouples arranged around a uniform temperature measuring region, and the thermoelectric reference junctions of the thermocouples arranged around a uniform temperature thermoelectric reference region. The differential thermal analysis sensor can be used for single-sample heat flux differential thermal analysis measurements, dual-sample heat flux differential thermal analysis measurements, or power compensation differential thermal analysis measurements.

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Wilmington, DE, United States of America

John W Schaefer