FANUC DPRNT measurement reports: field digits, rounding and decision precision
Using the 16i/18i-MB external output commands, distinguish variable precision from printed-field precision. Near-limit deviations and insufficient integer fields show how an apparently normal report can lose information needed for acceptance decisions.
Contents
A measurement retained in a macro variable is not necessarily preserved in full by an exported report. DPRNT has both number-format and character-output rules. When a report supports acceptance decisions, distinguish the value stored in the variable from the text that is visible.
The two format digits do not form one field-width number
The 16i/160i/160is-MB and 18i-MB/MB5 operator's manual GFZ/B-63534EN/02, §15.10, pages 436–439 (public mirror of the original manual) defines DPRNT as outputting characters and variable digits through the reader/punch interface. The format after a variable specifies integer digits and decimal places separately. For example, [43] means a 4-digit integer field and a 3-digit fractional field, not an output of 43 digits. This article applies to the cited edition's systems with the corresponding custom-macro and external-output functions; legacy interface rules are not treated as a newer network protocol.
Fewer decimal places can merge different measurements
In this original example, values are in mm: variable value 12.3456 becomes 12.346 when expressed to 3 decimal places. The measurement has not become more accurate; finer numerical information has been lost. The manufacturer's output example also demonstrates decimal rounding. New values are used here solely to explain its consequences.
| Deviation in variable/mm | Display to 3 decimal places | Original value compared with limit 0.010 |
|---|---|---|
| +0.0096 | +0.010 | Does not exceed limit |
| +0.0104 | +0.010 | Exceeds limit |
Two different conclusions produce the same text. If the receiver compares only the printed 0.010, the discarded difference cannot be recovered. Acceptance decisions and report formatting must be designed together: for example, preserve original numerical precision and an explicit decision result separately, instead of trying to reconstruct them from shortened text later.
An insufficient integer field is more than a cosmetic problem
The manufacturer's example in this edition also shows high-order digits being lost when the integer field is too short. Do not assume that a value too large for the field must produce an obvious error indication. Design the format for the value range and signs, rather than selecting digits from the current sample alone. A reported value within the normal range does not prove that the source variable was within that range.
Leading zeros may also be omitted or represented by spaces, and the positive-sign position depends on output settings. A receiver relying on fixed character columns must match the actual output format. A tag-based parser must likewise distinguish tags, minus signs, decimal points and record terminators.
Validating the data format does not validate measurement capability
Known test values that do not command machine motion can cover positive and negative values, decimals near limits and the largest expected integer field. Compare the variable with received text case by case. This checks representation rules in the data path. Probe repeatability, coordinate datum, temperature and measuring-instrument uncertainty are separate measurement issues; printing more digits does not solve them. More macro and data-function resources are in the OPTION section.