Thermal control system for controlling the temperature of a fluid
The invention relates to a thermal control system for controlling the temperature of a fluid. In particular, the invention relates to a control system having at least two heating elements, at least one of which is used for directly or indirectly heating a fluid, and at least one of which is used for heating a thermal probe used to determine the temperature of the fluid. The heating systems are controlled by at least one feedback controller.
1. A thermal control system for controlling a temperature of a fluid, comprising:
a biological fluid having a thermal mass;
a cartridge comprising:
a thermally conductive substrate having a thermal mass in thermal contact with the fluid;
and an instrument comprising:
a first heating element configured to contact said substrate and configured to heat said fluid;
a temperature sensing probe configured to measure the temperature of said fluid and comprising: a temperature sensing probe tip having a thermal mass, a thermistor, and a second heating element comprising a resistor located in the tip of the temperature sensing probe beneath the thermistor and configured for heating the probe tip and compensating heat lost from the probe; and
a feedback controller as part of the thermal control system for maintaining the temperature of the fluid as measured by the temperature sensing probe within a preselected range by controlling a current applied to at least one of the first or second heating elements, and wherein the temperature sensing probe tip has a thermal mass;
wherein the thermal mass of the temperature sensing probe tip is greater than the thermal mass of said fluid.
2. The control system of claim 1 , wherein the temperature sensing probe indirectly measures the temperature of said fluid by measuring a temperature of the substrate.
3. The control system of claim 1 , further comprising at least one electrochemical sensor located on the substrate and contacting said fluid.
4. The control system of claim 3 , wherein the at least one electrochemical sensor is configured to make potentiometric, amperometric, or a conductometric measurement of the fluid.
5. The control system of claim 3 , wherein the fluid has a volume from 1.mu.L to 1 mL.
6. The control system of claim 1 , further comprising electrical contacts for connecting to said first heating element and delivering current to said first heating element.
7. The control system of claim 6 , wherein the current delivered to said first heating element is delivered by a battery.
8. The control system of claim 1 , wherein the substrate is selected from the group consisting of silicon, glass, plastic and alumina.
9. The control system of claim 1 , wherein the substrate has a metal coated bottom.
10. The control system of claim 9 , wherein said metal comprises titanium tungsten alloy.
11. The control system of claim 1 , wherein the temperature sensing probe tip is made of aluminum.
12. The control system of claim 1 , wherein the fluid is housed in a conduit insulated on at least one side by plastic.
13. The control system of claim 1 , wherein the fluid is selected from the group consisting of a calibration fluid, a reagent containing fluid, a wash fluid, blood, plasma, serum, urine, cerebrospinal fluid, and diluted and amended forms thereof.
14. The control system of claim 1 , wherein the system is configured to maintain the temperature of the fluid within a range of ±0.2° C.
15. The control system of claim 1 , wherein the temperature of the fluid is maintained between 25° C.-60° C.
16. The control system of claim 1 , wherein the substrate is less than 1 mm thick.
17. The control system of claim 1 , further comprising a pump for displacing said fluid from said substrate and positioning a second fluid over said substrate.
18. The control system of claim 1 , further comprising a pump configured for moving the biological fluid.