| specifications | R841 | R851 | R861 |
| Work elements | Ultrasonic | Ultrasonic | Laser |
| Measuring Range | 0.5~20m | Single Unit:0.5~20m(20inch~65feet) | 0.3~60m |
| 20inch~65feet | Double Unit:1.0~60m(36inch~197feet) | ||
| Accuracy | ±1% | ±1% | ±2mm |
| Measure In Imperial Metric | √ | √ | √ |
| Operation Condition | 0~40℃ 30~70%RH | 0~40℃ 30~70%RH | 0~40℃ |
| Measureement function | Length,Area,Volume | Length,Area,Volume | Length,Area,Volume |
| Pythagorean Theorem | |||
| Data Store/recall | √ | √ | √ |
| Laser Class | 2 | 2 | 2 |
| Triangulation Measurement | √ | ||
| Low Battery Indication | √ | √ | √ |
| Sum Of Length | √ | √ | √ |
| Auto/Manual Shut Off | √ | √ | √ |
| LCD Backlight Selection | √ | √ | √ |
| Measuring Benchmark Setup | √ | √ | √ |
| Key Sound Beeps For Wrong | √ | √ | √ |
| Reading And Reading Confirmation | √ | √ | √ |
| General Characteristics | |||
| Power | 9V Alkaline Battery | 9V Alkaline Battery | 2x1.5V LR6(AA) |
| Product Weight | 205g | 315g | 217g |
| Product Size | 150mmx75mmx46mm | 150mmx75mmx46mm | 129mmx69mmx40mm |
Source: https://www.meterstesters.com/products/ultrasonic-distance-meters/ultrasonic-range-finder-r851.html