威特TC1600速测仪的实验室测试

Laboratory Testing of the Wild Tachymat TC 1600

作者对一台威特TC1600 速测仪进行了调制频率、加常数与温度、电压的关系试验。当温度在-10℃～+50℃之间变化时,实测频率与显示频率之差的变化量平均为±1.4Hz(或±0.1 ppm),加常数没有显著变化(仅为 ±0.23mm)。电压变化对频率和加常数没有明显影响。此外进行了加常数与信号强度关系的试验。在信号很弱时其最大变化量为1mm。在野外条件下产生的比例误差不超过0.5ppm,在频率—温度试验中采用了仪器的内部温度与显示频率。内部温度与外界温度之差在0℃～+11.5℃之间变化。预热对频率和加常数的影响分别为每30分钟 0.2ppm和每100分钟0.24mm,亦可忽略。TC1600在DIST即精测状态下单个观测值的标准差为±0.5mm,在野外试验基线场上根据4至8个距离值计算的平均标准差为±(0.4mm+0.4ppm),短周期误差随距离而变化,但均未超过1mm。

The modulation frequency and additive constant of an electronic tacheometer WildTachymat TC 1600 were tested versus temperature and supply voltage. The differencesbetween measured and predicted frequencies did vary by only ±1.4 Hz (or±0.1ppm)from the average difference across the entire temperature range from - 10℃to + 50℃. Thevariation of the additive constant over the same temperature range was very small(±0.23mm) and statistically insignificant. No significant effects of supply voltage on freque-ncy and additive constant were found. In addition, the additive constant was tested versussignal strength. Changes of 1 mm maximum were found at very low signal strengthscreating scale errors of less than 0.5ppm under field conditions. When establishing thefrequency-versus-temperature characteristic, full use was made of the accessibility ofinternally measured temperatures and internally computed predicted frequencies. Internaltemperatures differ between 0 and + 11.5℃ from ambient temperatures, depending onlength of operation, previous temperature exposure and present temperature. The warm-up effects on the difference frequency and the additive constant were also insignificantwith 0.2ppm per 30 min. and 0.24mm per 100 min., respectively. A standard deviationof a single TC 1600 distance observation ('DIST' mode) of±0.5mm was found dur-ing laboratory tests. On an EDM calibration baseline, average standard deviations of(±0.4mm + 0.4ppm) were realized for means of 4 to 8 distance measurements. Shortperiodic errors were found to change with distance but did not exceed 1 mm amplitude.