Product description and pin outs

Technical description

The PI 7-3 automatically recognises the probe type, determines the probe status, which is either triggered or seated (armed), and transmits debounced signals to the CMM controller. Status and control signals are transferred between the PI 7-3 interface, other Renishaw equipment and the CMM controller via the product interconnection system (PICS) ports.The TP7M probe series employ silicon strain sensors to detect the small gauging forces applied to the stylus tip. There is no electronic processing in the probe and the sensors are connected directly to the interface via the Renishaw autojoint connector, the probe head and associated wiring. The sensor signals are amplified and the resultant ‘probe signals', proportional to changes of strain, are compared with reference voltages to determine the status of the probe.

The initial value of strain in the sensor structure will vary with the mass of the stylus and the orientation of the probe. At switch-on or following re-orientation of the probe on a movable head, a process known as ‘autozero' is used to rapidly null the strain to a zero reference level.

When the stylus contacts the workpiece, a change of strain occurs in the probe structure causing the probe signal voltage to exceed the trigger reference level. A probe trigger signal condition occurs by asserting SYNC on the PICS port. As stylus deflection increases, the probe signal voltage will exceed the halt reference level and HALT will be asserted on the PICS port. When the stylus backs-off the workpiece, the probe signal falls below the reference levels; SYNC and HALT are cleared to the seated state and the sensor outputs are nulled to the zero reference level in preparation for the next trigger. Debounce timers allow the motion characteristics to stabilise after the initial trigger and reseat events, to prevent spurious switching.

A solid state relay (SSR) equivalent of the SYNC output is provided for controllers requiring a voltage free contact at their probe input.

There is a choice of two levels of trigger sensitivity to allow the TP7M series to be used on a wide range of CMM types or in situations where the ambient vibration levels are not ideal.

Reset switch

Automatically, the probe will reset to the armed state when the PI 7-3 is powered up. Occasionally, it may be necessary to perform a manual reset, for example after changing the probe stylus.
Press the RESET button on the front panel for two seconds to reset the probe to the armed (seated) state.

The TP7M probe types may be recognised by the differences in appearance shown below.

Switch 5

With switch 5 DOWN, the SYNC, HALT and SSR outputs will go to the triggered state when the CMM controller or other Renishaw equipment asserts the PICS STOP line. Setting switch 5 UP disables the response.

Switch 6

The HALT output at the PICS connector is active low with switch 6 DOWN but may be inverted by selecting switch 6 UP.

Switch 7

Set switch 7 to the UP position for normal operation with the TP7M or kinematic probes (TP2, TP20 or TP6/TP6A). For fully integrated operation of the TP7M with the TP200 probe on the same installation, set switch 7 to the DOWN position to allow the HALT signals from the PI 200 interface to be automatically routed to the CMM controller when the probe is changed.