Signal transmission system for a measurement device

• US 20110002361A1
• Filed: 09/09/2010
• Published: 01/06/2011
• Est. Priority Date: 12/23/2002
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: Woollett, Martin, Liptrot, John, Styles, John
• Granted Patent: US 9,140,547 B2
• Time in Patent Office: Days
• US Class Current: 375/133
• CPC Class Codes: G01B 21/047 Accessories, e.g. for positioning, for tool-setting, for measuring probes
• CPC Class Codes: G01B 2210/58 Wireless transmission of information between a sensor or probe and a control or evaluation unit
• CPC Class Codes: H04B 1/713 using frequency hopping

Abstract

A transmission system for a measurement device on a coordinate positioning apparatus comprises a station mounted on the measuring device and another station mounted on the coordinate positioning apparatus, wherein the station and the another station communicate with each other using a spread spectrum radio link, for example, frequency hopping. The station on the probe sends a regular signal and on receiving the signal the another station on the coordinate positioning apparatus synchronises its clock and sends an acknowledgement signal. Measurement data is either sent in the regular signal or in a measurement event driven signal.

Claims

1. A measurement apparatus, comprising;

a measurement probe comprising a first station, and

a coordinate positioning apparatus comprising a second station,

wherein the first station and the second station communicate with one another using a spread spectrum radio link,

the first station is operable in a normal mode for transmitting information relating to measurement events and in a power saving mode in which a request signal is periodically transmitted, and

when the first station is operating in the power saving mode, the second station responds to the request signal by transmitting a signal that instructs the first station to enter the normal mode.

2. The apparatus according to claim 1, wherein a first station periodically transmits a regular signal when operating in the normal mode.

3. The apparatus according to claim 2, wherein a rate of transmission of request signals in the power saving mode is slower than a rate of transmission of regular signals in the normal mode.

4. The apparatus according to claim 3, wherein the spread spectrum radio link is a frequency hopping spread spectrum link in which the first station hops between different frequency channels, and a frequency hopping rate in the power saving mode is slower than a frequency hopping rate in the normal mode.

5. The apparatus according to claim 1, wherein the first station communicates with the second station via a direct sequence spread spectrum radio link.

6. The apparatus according to claim 1, wherein the signal transmitted by the second station that instructs the first station to enter the normal mode comprises an affirmative signal, and the second station can alternatively transmit a negative signal in response to the request signal that instructs the first station to remain in the power saving mode.

7. The apparatus according to claim 1, wherein

the first station, when operating in the normal mode, transmits information relating to measurement events occurring at the measurement probe,

the second station receives the information relating to each measurement event and generates a corresponding output signal, and

a time delay between each measurement event that occurs at the measurement probe and the corresponding output signal generated at the second station is substantially constant.

8. The apparatus according to claim 7, wherein the measurement probe comprises a touch trigger probe and the information relating to measurement events comprises trigger signals.

9. The apparatus according to claim 1, wherein the first station comprises a master clock and the second station recovers the master clock from signals transmitted by the first station.

10. The apparatus according to claim 1, wherein the measurement probe comprises a battery, and the measurement probe is powered by the battery.

11. The apparatus according to claim 1, wherein the first station has an identity code and the second station is set to only communicate with the first station having the identity code.

12. A transmission system for a measurement device for a coordinate positioning apparatus, comprising:

a first station for mounting with one of the measurement device and the coordinate positioning apparatus; and

a second station for mounting with the other of the measurement device and the coordinate positioning apparatus;

wherein the first station and the second station communicate with one another using a spread spectrum radio link,

the first station can be placed in a normal mode or in a power saving mode that consumes less power than the normal mode,

the first station transmits regular signals in the power saving mode and each regular signal asks if the first station should change mode, and

the first station changes mode to the normal mode when the first station receives an affirmative response from the second station.

13. The transmission system according to claim 12, wherein

the spread spectrum radio link is a frequency hopping spread spectrum link,

the first station hops between frequency channels, and

frequency hopping occurs at a slower rate when in the power saving mode than when in the normal mode.

14. The transmission system according to claim 12, wherein the spread spectrum radio link is a direct sequence spread spectrum link.

15. The transmission system according to claim 12, wherein if a signal transmitted by the first station is not adequately received by the second station, the signal is retransmitted by the first station.

16. The transmission system according to claim 12, wherein, when the second station receives a signal transmitted by the first station, the second station transmits an acknowledgement signal, and

the first station comprises a radio modem that is turned off when the first station receives the acknowledgement signal from the second station.

17. The transmission system according to claim 12, wherein

the first station is mounted with the measurement device,

when a signal transmitted by the first station in the normal mode contains information relating to a measurement event, the second station produces a measurement device output signal after a time delay, and

the time delay is substantially constant and chosen so that the time delay is long enough to allow retransmissions of the signal within the time delay.

18. The transmission system according to claim 12, wherein the first station has an identity code and the second station is set to only communicate with the first station having the identity code.

19. The transmission system according to claim 12, wherein the first station is provided with a mode in which the first station transmits a signal containing an identity code for the first station and the second station is provided with a mode in which, on receiving the signal containing the identity codes for the first station, the second station is set to only communicate with the first station having the identity code.

20. A measurement apparatus, comprising;

a measurement probe comprising a first station, and

a coordinate positioning apparatus comprising a second station,

wherein the first station communicates with the second station via a spread spectrum radio link,

the first station is arranged to transmit a message to the second station at a first power level, and

if the second station does not receive the message, the message is retransmitted by the first station at a second power level, the second power level being higher than the first power level.