Zero check

Zero/span check Zero check 0.005 ppm Span check 0.08-0.10 on a 1.0-ppm full scale daily... 

The micrometers and calipers must be zero-checked before use and regularly checked against standard test blocks. Standard tests for taking dimensions include ... 

Analytical Procedure. In your notebook draw up a work sheet, similar to that in Table 6.1, including standard solutions, standard checks, blanks and extracts, ending with a final standard check and zero check . 

Put one into the colorimeter and set the reading to zero. Measure the absorbance of the other one and keep that one as the zero check . 

Continue to read and record the absorbance of all the standard, blank and sample solutions. After every 10 absorbance readings, measure the absorbance of a standard check and use the zero check cuvette to check the zero setting. 

This indicates that the residual sum of squares for the individual is near zero. Check the initial value of the residual error and see if it is small. If so, increase its value. Alternatively, try fitting the logarithms of the concentration with an additive residual error model. 

Decide by inspection whether the following reactions will have values of AS which are positive, negative, or about zero. Check values from Appendix III. 

When the solver performed an illegal operation, such as a divide by zero, check whether the equations can be modified/transformed to avoid this error. Inspect whether different initial conditions or stricter bounds avoid premature termination of the algorithm. 

In the peak-detecting mode the insertion of zero samples is not necessary because peaks are always followed by a zero (wash) reference. However, to detect possible contamination of the wash solution, a zero check is recommended at intervals (fe, every 3-4 calibrations). Standards should be inserted more frequently as compared with the steady-state mode, Le., about every lO or 20 sample. 

If the impeller has suffered substantial erosion, pumping capacity will decrease. Not infrequently, the motor comes loose from the shaft, and pumping capacity falls to essentially zero. Check the driver motor with an ammeter. Low amperage indicates the impeller is no longer fixed to the shaft. 

After measuring absorbances for a test solution, check the blank standard. If this does not read zero, check the system and then repeat steps 12.2 through 12.5. 

Then at each point, check which of the inequahty constraints are active, or exactly equal to zero. These can be placed into the active set and treated as equahties. The remaining can be put aside to be used only for testing. A step can then be proposed using the GRG algorithm. If it does not cause one to violate any of the inactive inequality constraints, the step is taken. Otherwise one can add the closest inactive inequality constraint to the active set. Finding the closet inactive equahty will almost certainly require a hne search in the direc tion proposed by the GRG algorithm. 

Corrective action Do multipoint calibration invalidate data collection since last zero/ span check within control limits... 

Check continuity zero and adjust Calibrate as required Chemical Cleaning Activation Passivation Rinse... 

The manufacturer s instructions for operating a combustible gas indicator should be carefully reviewed before the device is used. In general, all explosimeters require a brief initial warm-up period so that the batteries can heat the filaments. Then battery strength should be checked, and the zero scale adjusted. When zero is established and the indicating needle is stable, the instrument is ready for use. 

Releases of Less Than One Pound. Total annual releases or off-site transfers of a toxic chemical from the facility of less than 1 pound may be reported in one of several ways. You should round the value to the nearest pound. If the estimate is 0.5 pounds or greater, you should either check the range bracket of"1-499 in column A.1 orenterTin column A.2. J2a not use both oolumns A. 1 and A.2. If the release is less than 0.5 pounds, you may round to zero and check the "0 bracket in A.t. 

The Waters company recommends a system check of the chromatographic equipment that is used for plate number determination and analyses (2) the columns in the GPC unit used are replaced by a zero dead volume union. Then the test sample is injected under the same conditions such as a plate number determination. The 5a peak width measured on a suitable recorded peak is evaluated this 5or width of a 20-/a1 injection should be lower than 150 /a1. 

If applicable, the program notes that there is an imaginary frequency present just prior to the frequency and normal modes output, and the first frequency value is less than zero. Log files may be searched for this line as a quick check for imaginary frequencies. 

To remove water, commercial ionic liquids used for fundamental research purposes should be dried at 60 °C in vacuo overnight. The water content should be checked prior to use. This can be done qualitatively by infrared spectroscopy or cyclovoltametric measurements, or quantitatively by Karl-Fischer titration. If the ionic liquids cannot be dried to zero water content for any reason, the water content should always be mentioned in all descriptions and documentation of the experiments to allow proper interpretation of the results obtained. 

Set the dial indicator to zero. Completely loosen the hold-down nut on the foot to be checked. Watch the dial indicator closely for foot movement during the loosening process. 

---