ISO 11171:2010 pdf free download – Hydraulic fluid power一Calibration of automatic particle counters for liquids.
The final dilution of the polystyrene latex sphere suspension which is actually counted shall be clear in appearance. Cloudiness in the samples is evidence of insufficient dilution and shall be corrected before proceeding.
D.3 Set the APC to the differential mode. Use the calibration curve (see Clause 6) to estimate the threshold setting that corresponds to the polystyrene latex sphere size, as follows:
a) set the first channel to 1 ,5 times the threshold noise level of the APC;
b) set the third channel to the threshold voltage setting corresponding to the polystyrene latex sphere size;
c) set the second channel to the threshold voltage setting corresponding to 0,72 times the threshold voltage setting of the third channel;
d) set the fourth channel to the threshold voltage setting corresponding to 1,32 times the threshold voltage setting of the third channel.
Only the differential particle counts of the second and third channels are used.
NOTE 1 D.3, D.4 and D.5 specify the moving-window differential half-count method for determining the threshold setting that corresponds to the median polystyrene latex sphere size. These data are critical to determining sensor resolution. Inaccurate determination of the threshold setting corresponding to the median polystyrene latex sphere size can result in apparently poor sensor resolution and failure of the APC to pass the sensor performance specification.
NOTE 2 Due to differences in the optical properties of the polystyrene latex spheres and the calibration dust (4.4), the apparent particle size obtained using an APC calibrated in accordance with this International Standard differs from the size stated by the supplier of the polystyrene latex spheres. As a first approximation, choose a particle size that is 10 % to 50 % larger than the particle size stated by the supplier of the polystyrene latex spheres.
NOTE 3 To determine the half-count setting more rapidly, perform D.3 to 0.5, but obtain only one count (instead of five as indicated in D.4) of at least 500 particles in the second channel. Readjust the channels as necessary and repeat the process until the half-count condition described in D.6 is achieved. Following this, repeat D.3 to D.6 using five counts as described in D.4.
D.4 Disperse the diluted polystyrene latex sphere sample by mechanical shaking for at least 1 mm. Degas the sample under vacuum or ultrasonically until the bubbles rise to the surface. Obtain five consecutive particle counts, each consisting of at least 10 ml and 2 500 particles in the second channel. Evaluate the particle count data using the criteria described in 6.3. If DQ is less than the appropriate value shown in Table C.2, proceed to D.5. If not, discard the data and suspect an error in the analytical technique. Repeat D.2 to D.4 after taking appropriate corrective action (see Note to 6.3).
D.5 Calculate the difference, D, expressed as a percentage, between the second and third channels using Equation (D.2):
N2 is the mean number of particles counted for the second channel;
N3 is the mean number of particles counted for the third channel.
If the absolute value of D is less than or equal to 3 %, the threshold setting of the third channel corresponds to the size of the polystyrene latex sphere. In this case, proceed to D.6. If not, and if the value of D is negative, the threshold settings in D.3 are too high. If D is positive, the threshold settings in D.3 are too low. Repeat D.3 to D.5 using threshold settings for the second, third and fourth channel which have been readjusted. If no threshold setting yields an absolute value for D less than 3 %, the threshold setting of the third channel yielding the minimum absolute value of D corresponds to the size of the polystyrene latex sphere.