Reading and Interpreting Tolerances
Why is the tolerance given as two parts that must be added together?
While most of the accuracy of the instrument reading is proportional to the displayed value, sometimes an accuracy characterized in that way makes no sense.
A reading of zero (on any scale) will have a "ppm of Reading" value of zero and will therefore be rated as perfectly accurate. This is just not possible.
| Accuracy1 [ppm of Reading (ppm of Reading for Option 002) + ppm of Range] | |||||
|---|---|---|---|---|---|
| Range | 24 Hour2 | 90 Day3 | 1 Year3 | 2 Year3 | |
| 100 μV | 2.5 + 3 | 5.0 (3.5) + 3 | 9 (5) + 3 | 14 (10) + 3 | |
| 1 V | 1.5 + 0.3 | 4.6 (3.1) + 0.3 | 8 (4) + 0.3 | 14 (10) + 0.3 | |
| 10 V | 0.5 + 0.05 | 4.1 (2.6) + 0.05 | 8 (4) + 0.05 | 14 (10) + 0.05 | |
| 100 V | 2.5 + 0.3 | 6.0 (4.5) + 0.3 | 10 (6) + 0.3 | 14 (10) + 0.3 | |
| 1000 V4 | 2.5 + 0.1 | 6.0 (4.5) + 0.1 | 10 (6) + 0.1 | 14 (10) + 0.1 | |
1 Specifications are for PRESET; NPLC 100
2 For fixed range (> 4 min.) MATH NULL and T cal ± 1 ° C.
3 Specifications for 90 day, 1 year and 2 years are within 24 hours and ± 1 °C of last ACAL; T cal ± 5 ° MATH NULL and fixed range. Ppm of Reading specifications for High Stability (Option 002) are in parentheses. Without MATH NULL, add 0.15 ppm of Range to 10V, 0.7 ppm without MATH NULL, and for fixed range less than 4 minutes add 0.25 ppm of Range to 10V, 1.7 ppm of Range to 1V and 17 ppm of Range to 0.1V. Add 2 ppm of reading additional error for factory traceability to US NIST. Traceability error is the absolute error relative to National Standards associated with the source of last external calibration.
4 Add 12 ppm X (√in/1000)2 additional error for inputs > 1000