| Temperature Sensor |
| Operation Range | U23-001A internal sensor: -40 to 70°C (-40 to 158°F)
U23-002A external temperature sensor: -40 to 70°C (-40 to 158°F)
U23-003 and U23-004 external sensors: -40 to 100°C (-40 to 212°F), with tip and cable immersion in fresh water up to 50°C (122°F) for one year |
| Accuracy | U23-001A and U23-002A: ±0.25°C from -40 to 0°C (±0.45 from -40 to 32°F), ±0.2°C from 0 to 70°C (±0.36 from 32 to 158°F)
U23-003 and U23-004: ±0.21°C from 0° to 50°C (±0.38°F from 32° to 122°F); see Plot A |
| Resolution | U23-001A and U23-002A: 0.04°C (0.072°F)
U23-003 and U23-004: 0.02°C at 25°C (0.04°F at 77°F); see Plot A |
Response Time
(Typical to 90%) | U23-001A internal sensor: 10 minutes in air moving 1 m/sec
U23-002A external temperature sensor: 3 minutes, 45 seconds in air moving 1 m/sec
U23-003 and U23-004 external sensors: 3 minutes in air moving
1 m/sec; 30 seconds in stirred water |
| Drift | U23-001A and U23-002A: <0.01°C (0.018°F) per year
U23-003 and U23-004: <0.1°C (0.18°F) per year |
| Relative Humidity Sensor (U23-001A, U23-002A only) |
| Operation Range | 0 to 100% RH, -40° to 70°C (-40° to 158°F)
Exposure to conditions below -20°C (-4°F) or above 95% RH may temporarily increase the maximum RH sensor error by an additional 1% |
| Accuracy | ±2.5% from 10% to 90% RH typical to a maximum of ±3.5% including hysteresis at 25°C (77°F); below 10% and above 90% ±5% typical |
| Resolution | 0.05% |
Response Time
(Typical to 90%) | U23-001A: 40 minutes in air moving 1 m/sec with protective cap
U23-002A: 15 seconds in air moving 1 m/sec |
| Drift | <1% per year typical |
| Logger |
| Operation Range | -40° to 70°C (-40° to 158°F) |
| Real-time Clock | ±1 minute per month 0° to 50°C (32° to 122°F) |
| Battery | 1/2 AA, 3.6 Volt lithium, user-replaceable (HP-B) |
| Battery Life (Typical Use) | 3 years with 1 minute or greater logging interval |
| Memory (Non-Volatile) | 64K bytes memory (approx. 21,000 temperature and RH measurements) |
| Materials | All models: ASA styrene polymer housing and mounting clamp; polypropylene protective cap; Buna-N o-ring(s); U23-001A,
U23-002A only: ASA styrene polymer RH sensor cap; modified hydrophobic polyethersulfone membrane |
| Cables | U23-001A: No cables
U23-002A: One 184 cm (6 ft) PVC cable; sensor diameter 1 cm (0.38 in.)
U23-003: Two 184 cm (6 ft) PVC cables; sensor diameter 0.5 cm (0.20 in.)
U23-004: One 184 cm (6 ft) PVC cable; sensor diameter 0.5 cm (0.20 in.) |
| Environmental Rating | Electronics housing is NEMA 6P equivalent (tolerant of brief submergence);
Units with RH sensors are NEMA 4 equivalent (splash-resistant) |
| Launch Modes | Immediate start; delayed start |
| Logging Interval | Fixed-rate or multiple logging intervals, with up to 8 user-defined logging intervals and durations; logging intervals from 1 second to 18 hours |
| Offload Modes | Offload while logging; stop and offload |
| Battery Indication | Battery voltage can be viewed in status screen and optionally logged in datafile. Low battery indication in datafile. |
| Weight | U23-001A: 57 g (1.5 oz); U23-002A: 118 g (3.1 oz); U23-003: 138 g (3.7 oz); U23-004: 102 g (2.7 oz) |
| Dimensions | Housing measures 10.2 × 3.8 cm (4.0 × 1.5 in.) |
| NIST Certificate | Temperature certificate available for additional charge |
 | The CE Marking identifies this product as complying with all relevant directives in the European Union (EU). |