Probe Termination Pin set height is a
critical factor in the performance and
life of the X Probe. When set too low,
the X Probe is under-stroked, reducing
the contact force and the X Probe's ability
to penetrate surface contaminants. When
set too high, the X Probe is over-stroked,
resulting in decreased spring life or
possible tip damage due to bottoming.
To calculate proper set height, follow
these steps:
- Make a cross-sectional sketch of the
fixture in the actuated position. The
sketch at right is typical of many vacuum
fixtures.
- Dimension the thickness of the items
that stack up on the top surface of
the probe mounting plate. Add these
dimensions to get a final distance (H)
from the top of the plate to the contact
surface of the UUT. Subtract the average
lead length from this dimension if contacting
leaded components.
- (A) is the distance from the UUT to
the top of the back plate.
- (C) is the X Probe tube length (see
table).
- (P) is the distance from the X Probe
tip to the top of the X Probe tube (see
table). Remember this dimension is with
the X probe compressed to its recommended
working travel.
(A) = (H) + .375(9.53) (probe
plate) + .563(14.29) (optional spacer
plate). Use actual plate thickness or
standoff lengths as per your design.
Proper set height = (A) - (C) - (P)
Example for X39-25 Series:
H = Spacer + Support Plate
+ Board Stop
= .062(1.58) + .196(4.98) + .125(3.18)
= .383(9.74)
P = .105(2.67) (from table)
Set Height = (A) - (C) - (P)
1.321(33.55) - 1.178(29.92) - .105(2.67)
= .038(0.97)
| |
|
Series
|
X Probe
Tube Length C |
Recommended
Extension P |
| X39-25
|
1.178
(29.92) |
.105
(2.67) |
| X50-25
|
1.110
(28.19) |
.133
(3.38) |
| X50-40
|
1.110
(28.19) |
.133
(3.38) |
| X50-40-D*
|
1.110
(28.19) |
.283
(7.19) |
| X75-25
|
1.100
(27.94) |
.143
(3.63) |
| X75-40
|
1.100
(27.94) |
.143
(3.63) |
| X75-40-D*
|
1.100
(27.94) |
.293
(7.44) |
| All
dimensions are in inches (mm)
|
Related Notes:
To mix X Probe series within
a fixture, calculate the proper set height
for each series used in the fixture.
Thicker mounting plates allow the greatest
set height range, but hole straightness
may suffer.
For dual level testing, .400(10.16 mm)
stroke X Probes are mounted in the same
sockets, at the same set height, as standard
.250(6.35 mm) stroke X Probes. As a result,
they can be interchanged freely from one
socket to another as test needs dictate.
|
