Strainoptics PS-100-SF User manual

Strainoptics PS-100-SF
Polarimeter
Quick-Start Guide
Tardy Method (Analyzer Rotation)
Note: These instructions are not meant to replace the full Strainoptics PS-100-SF instruction manual
supplied with your polarimeter. If you are not yet familiar with the initial setup, general operation, and
maintenance requirements of your instrument, or if questions arise, please refer to the complete manual
for further details. Before proceeding, we recommend that you become familiar with the names of the
various instrument components as shown in the illustration below.
1. Configure the instrument for CIRCULAR polarization as follows:
a. Verify that the Polarizer plate (not shown) is installed with the nameplate “CIRCULAR” facing
up.
b. Loosen the Analyzer Scale Lock (L). Using the Rotation Handle (H), rotate the Analyzer Scale
(S) until the number “1” on the Analyzer Scale lines up with the Analyzer Scale Lock (L). The
Reference Mark (R) should be adjacent to the number “-45” on the Protractor Scale (PS).
Tighten the Analyzer Scale Lock.
c. Using the Analyzer Knobs (K), rotate the Analyzer (A) so that the Index Marks (I) are aligned
with the number “1” and “0” on the Analyzer Scale.
d. Move the P-C handle (PC) to the “C” position (under the Rotation Handle).
2. Turn on the illuminator. When looking through the Analyzer, the field will be dark. Place the sample to
be measured on the Polarizer plate.
Strainoptics, Inc.
www.strainoptics.com (Continued on other side)
In order to calculate stress in your material, you must first know its thickness in millimeters
and its material stress constant in Brewsters. In order to use the Tardy Method of analyzer
rotation, you must first know or be able to determine the direction of principal stresses at the
point of interest. See the PS-100 instruction manual for further details.
H. Rotation Handle
S. Analyzer Scale
L. Analyzer Scale Lock
R
. Reference Mark
(set scale to -45º)
PS. Protractor Scale
K.
Analyzer
Knob
A. Analyzer
I.
Index
Marks
PC. P-C Handle

PS-100-SF (Tardy) Quick-Start Guide, Continued
3. Using a felt-tip pen, mark the area around the point of interest (POI) on the sample. Position the
sample in the correct orientation for measurement as follows:
a. Identify the direction of the principal stress being measured. If unknown, refer to the PS-100-SF
instruction manual to determine direction, or use the SENARMONT method of analyzer rotation
instead.
b. Position the sample with the direction of principal stress being measured parallel to the
analyzer-polarizer axes (45º to the reference mark of the polarimeter),
c. Follow the instructions for analyzer rotation below and repeat above steps for each POI and
direction desired.
4. If there is stress present in the sample, it will be seen through the analyzer as varying shapes and
colors (fringes). The shape and color of the fringes indicate the distribution and magnitude of the
stresses. (Very low stresses will appear white or gray.) Identify the LOWER fringe order (n) closest to
the POI using the following table. For example, if gray is the color at the POI, then n = 0. Likewise, if
bright yellow, n = 0. If the color at the POI is blue, then n = 1. Write this value down.n = ___
Color at POI Fringe
Order
Black 0
-Gray
-White->Yellow
-Bright Yellow
-Orange (dark yellow)
-Red
Indigo->Violet 1
-Blue
-Blue->Green
-Green->Yellow
-Yellow
-Orange (dark yellow)
-Red
Indigo->Violet 2
-Green
-Green->Yellow
-Pink
Violet 3
-Green
5. From Step 4, note the HIGHER fringe order closest to the POI. This would be n+1. For example,
if the lower fringe order (n) is 0, then the higher fringe order would equal 1.
6. While observing the movement of the fringes in the sample, rotate the Analyzer CLOCKWISE until
a fringe is centered on the POI. Read the fractional fringe order (f) from the Analyzer
Scale. This value will be between 0.0 and 1.0. Write this value down. f = ___
7. If you observed in Step 6 that a LOWER order fringe (see table) has moved TOWARD the POI,
calculate the fringe order (N) at the POI using the values from Step 4 and Step 6 in this relation:
N = n+f Write this value down. The stress measured at the POI is in tension (+).
8. If you observed in Step 6 that a HIGHER order fringe (see table) has moved TOWARD the POI,
calculate the fringe order (N) at the POI using the values from Step 4 and Step 6 in this relation:
N = (n+1)-f Write this value down. The stress measured at the POI is in compression (-).
9. To calculate the measured stress in MPa , use the following relation:
Where:
S = Stress (MPa) Note: Multiply by 145 to arrive at PSI.
N = Fringe order at POI
λ= Wavelength (565 nm for glass; 570 nm for plastic)
T = Thickness of material at POI, in mm
CB= Material constant, Brewsters (2.65 for soda-lime glass)
R = Retardation (nm)
Strainoptics, Inc. 108 West Montgomery Ave. ٠North Wales, PA 19454 ٠Tel: [phone]Fax: [phone]
E-mail: st[email protected] ٠www.strainoptics.com
Decreasing Intensity =
Higher Stress
N * λ
T * CBR
T * CB
S =
=