High dynamic range analog-to-digital converter

• US 6,737,642 B2
• Filed: 03/18/2002
• Issued: 05/18/2004
• Est. Priority Date: 03/18/2002
• Status: Expired due to Term

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Syagen Technology, Inc. (Safran SA)
• Inventors: Syage, Jack A., Hanning-Lee, Mark A.
• Primary Examiner(s): Wells, Nikita
• Application Number:
  US10/101,670
• Publication Number:
  US 20030173514A1
• Time in Patent Office: 792 Days
• Field of Search: 250/287, 250/281, 250/283, 250/286, 250/397
• US Class Current: 250/287
• CPC Class Codes: H01J 49/0036 Step by step routines describing the handling of the data generated during a measurement
• CPC Class Codes: H01J 49/025 Detectors specially adapted to particle spectrometers data acquisition H01J49/0036; detectors per se G01T, e.g. G01T1/28, G01T1/29
• CPC Class Codes: H03M 1/186 in feedforward mode, i.e. by determining the range to be selected directly from the input signal

Abstract

A high speed analog to digital converter (“ADC”) that can be used in a detector system. The ADC is coupled to a detector and a processor. The detector generates an analog signal in response to the detection of a trace sample, such as an ionized molecule or a beam of light. The processor determines a baseline value and threshold value. Portions of the analog signal at or below the threshold are assigned the baseline value. The threshold typically corresponds to a value above the noise level in the system. The detector thus removes undesirable noise from the readout value. The process can compensate for factors such as DC drift while providing accurate data regarding detection of the trace sample.

Claims

1. A time of flight mass spectrometer, comprising:

an accelerator that accelerates an ionized sample;

a detector that provides an analog signal in response to detection of the ionized sample;

an analog to digital converter coupled to said detector; and

,

a processor connected to said analog to digital converter, said processor computes a baseline value and a threshold value of the analog signal and assigns the baseline value to the portions of the analog signal at or below the threshold value.

2. The mass spectrometer of claim 1, wherein the baseline value is zero.

3. The mass spectrometer of claim 1, wherein said processor adjust said analog to digital converter to output an intensity value of the analog signal if the analog signal exceeds the threshold value.

4. The mass spectrometer of claim 1, wherein a plurality of analog signals are binned to create a histogram.

5. The mass spectrometer of claim 1, wherein a plurality of analog signals are binned to determine a mean single-pulse intensity that is divided into an amplitude of the analog signal to determine a number of pulses.

6. The mass spectrometer of claim 1, wherein the baseline value is represented by an average value.

7. The mass spectrometer of claim 1, wherein the baseline value is represented by a linear ramp.

8. The mass spectrometer of claim 1, wherein the baseline value is represented by a higher-order polynomial function.

9. The mass spectrometer of claim 1, wherein the baseline value is filtered from the analog signal.

10. The mass spectrometer of claim 1, wherein the analog signal is compressed.

11. A time of flight mass spectrometer, comprising:

accelerator means for accelerating an ionized sample;

detector means for generating an analog signal in response to detection of the ionized sample;

analog to digital means for converting the analog signal to a digital bit string; and

,

processor means for computing a threshold value of the analog signal and assigning the baseline value to the portions of the analog signal at or below the threshold value.

12. The mass spectrometer of claim 11, wherein the baseline value is zero.

13. The mass spectrometer of claim 11, wherein said processor means adjust said analog to digital converter means to output an intensity value of the analog signal if the analog signal exceeds the threshold value.

14. The mass spectrometer of claim 11, wherein a plurality of analog signals are binned to create a histogram.

15. The mass spectrometer of claim 11, wherein a plurality of analog signals are binned to determine a mean single-pulse intensity that is divided into an amplitude of the analog signal to determine a number of pulses.

16. The mass spectrometer of claim 11, wherein the baseline value is represented by an average value.

17. The mass spectrometer of claim 11, wherein the baseline value is represented by a linear ramp.

18. The mass spectrometer of claim 11, wherein the baseline value is represented by a higher-order polynomial function.

19. The mass spectrometer of claim 11, wherein the baseline value is filtered from the analog signal.

20. The mass spectrometer of claim 11, wherein the analog signal is compressed.