X-ray analytical instrument with improved control of detector cooling and bias supply

Patent metadata

Field	Value
Publication number	US-10094936-B2
Application number	US-201514931921-A
Country	US
Kind code	B2
Filing date	Nov 4, 2015
Priority date	Nov 4, 2015
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

Disclosed is a circuit for controlling the temperature and the bias voltage of a detector used by an X-ray analytical instrument. The circuit uses a single common reference voltage for the temperature measurement and for all the ADCs and DACs in the circuit, resulting in reduced drift and improved reproducibility of detector temperature and bias voltage. ADCs with a larger number of bits are used to produce precision values of the temperature, the bias voltage, and their respective setpoints. The setpoints are digitally varied until the precision setpoint values correspond to desired values of temperature and bias setpoints.

First claim

What is claimed is:

1. A circuitry for controlling a cooling power supply providing cooling power to a cooling unit of a detector of an X-ray analyzer, the circuitry comprises:
a thermal measurement element producing a temperature measurement of the detector and subsequently a temperature voltage,
a pre-amplifier circuit providing a control signal for controlling the cooling power, the pre-amplifier circuit further comprises:
a single common reference element providing a common reference voltage,
a digital-to-analog converter (DAC) configured to produce a setpoint voltage based on a pre-determined setpoint temperature value,
an analog-to-digital converter (ADC) configured to digitize the temperature voltage and the setpoint voltage and produce a precision setpoint value, wherein the precision setpoint value is used to produce an adjusted setpoint voltage,
a comparator producing a differential value between the temperature voltage and the adjusted setpoint voltage wherein the differential value is used as a basis for the control signal, wherein the common reference voltage is referenced by the thermal measurement, the DAC and the ADC.

2. The circuitry of claim 1 wherein the ADC is referenced to the reference voltage.

3. The circuitry of claim 1 wherein the DAC is referenced to the reference voltage.

4. The circuitry of claim 1 wherein the thermal measurement element is referenced to the reference voltage.

5. The circuitry of claim 1 wherein the thermal measurement element comprises:
a thermistor electrically connected to ground at a thermistor first end and to a connection point at a thermistor second end,
a precision resistor electrically connected to the connection point at a resistor first end and to the reference voltage at a resistor second end, and,

wherein the temperature voltage is measured at the connection point.

6. The circuitry of claim 1 , wherein the pre-amplifier circuit is assembled on at least one circuit board.

7. The circuitry of claim 1 , wherein the comparator is a differential amplifier.

8. The circuitry of claim 1 wherein the ADC and the DAC each has a respective number of bits, and the ADC has a larger number of bits than the DAC.

9. The circuitry of claim 1 wherein the ADC is used to produce a precision temperature value.

10. The circuitry of claim 1 wherein the temperature voltage and the temperature setpoint voltage are both provided to the ADC as respective inputs, and the ADC comprises at least two independent analog-to-digital conversion channels, each used for the respective input.

11. The circuitry of claim 1 further comprises a setpoint verification module and the pre-amplifier circuit is electronically coupled with the verification module.

12. The circuitry of claim 11 wherein the verification module is an executable computer program code residing on a data processing unit.

13. The circuitry of claim 12 wherein the verification module is configured to execute iteratively for each iteration number of i, wherein i=1, 2, . . . , the steps of the program code including:
retrieving a desired precision temperature value PSV 0 , from the data processing unit,
retrieving an i th iteration of the precision setpoint value, PSV i ,
retrieving an i th iteration of the setpoint temperature value, SV i ,
calculating a digital precision setpoint error, Δ, given by Δ=PSV 0 −PSV i , wherein the differential value is the analog equivalent of the digital precision setpoint error,
setting the adjusted setpoint temperature value based on the precision setpoint error, thereby producing an (i+1) th iteration, SV i+1 , of the setpoint temperature value,
continuing the iteration with the next value of i.

14. A circuitry for providing a bias voltage via a bias power supply to a detector of an X-ray analyzer, the circuitry comprises:
a bias voltage measurement element producing a bias measurement voltage,
a pre-amplifier circuit providing a control signal for controlling the bias power supply, the pre-amplifier circuit further comprises:
a single common reference element providing a common reference voltage,
a bias digital-to-analog converter (DAC) configured to produce a setpoint voltage based on a pre-determined bias setpoint value and the reference voltage,
a bias analog-to-digital converter (ADC) configured to digitize the bias measurement voltage and the bias setpoint voltage and produce a precision bias setpoint value, wherein the precision bias setpoint value is used to produce an adjusted bias setpoint voltage,
a comparator producing a differential value between the bias voltage and the adjusted bias setpoint voltage wherein the differential value is used as a basis for the control signal, wherein the common reference voltage is referenced by the bias DAC and the bias ADC.

15. The circuitry of claim 14 wherein the precision bias setpoint value is used to adjust the bias setpoint value, which is further used to produce an adjusted bias setpoint voltage.

16. The circuitry of claim 14 wherein the bias measurement voltage is equal to the detector bias voltage multiplied by a divider ratio.

17. The circuitry of claim 16 wherein the divider ratio is equal to the resistance of a first smaller resistor divided by the sum of the resistances of the first resistor and a second larger resistor.

18. The circuitry of claim 14 wherein the bias voltage is determined by a bias regulator which is controlled by the control signal, and wherein the differential value is used as the control signal.

19. The circuitry of claim 14 , further comprises a bias setpoint verification module and the pre-amplifier circuit is electronically coupled with the bias setpoint verification module.

20. The circuitry of claim 19 wherein the verification module is an executable computer program code residing on a data processing unit.

Assignees

• Battyani Marc
• Olympus Scient Solutions Americas Inc

Inventors

• Battyani Marc

Classifications

• G01N2223/076

  X-ray fluorescence · CPC title

• G01N23/223

  by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence · CPC title

• G01N2223/3103

  cooling, cryostats · CPC title

• G01T1/175 Primary

  Power supply circuits · CPC title