The Senva CT1D-A3X is a duct-mount, single-channel NDIR carbon dioxide (CO2) transmitter for demand-controlled ventilation. It reports CO2 over selectable 4-20mA, 0-5V, or 0-10V outputs and includes an integrated solid-state setpoint relay for direct on/off ventilation control. This no-display configuration ships at the factory-default 0-2000 ppm range with a fixed setpoint; range, calibration offset, and setpoint thresholds are not field-adjustable without the LCD/menu option.
Specifications sourced from the Datasheet rev. 5/28/2024 (Senva doc #152-0381-0C).
Key Features
Technical Specifications
| Carbon Dioxide (CO2) | |
| Sensing Element | Non-Dispersive Infrared (NDIR) |
| Output Scaling | 0-2000 ppm (fixed) |
| Accuracy (Standard) | +/-(30 ppm + 3% of reading), 400-2000 ppm (at -10 to 50C, 0-85% RH). Fixed 0-2000 ppm range; higher ranges require the LCD/menu version. |
| Drift (ABC disabled) | 35 ppm/month |
| Auto-Calibration (ABC) | Selectable ON/OFF (default ON) |
| Pressure Dependency | +1% of reading per kPa from nominal (101 kPa) |
| Response Time | 60 s to 90% of reading |
| Sample / Update Rate | 1 s / 1 s |
| CO2 Element Life | 15+ years |
| Setpoint | Fixed at factory default (on 800 ppm / off 700 ppm); not field-adjustable |
| Setpoint Relay | |
| Type | Solid-state, 1A @ 30VAC/DC, N.O. |
| Power & Enclosure | |
| Power Supply | 24 VAC 100 mA max / 12-30 VDC 50 mA max (15-30 VDC or 24 VAC required for 0-10V output) |
| Enclosure | ABS / Polycarbonate, IP20 / NEMA 1, duct mount |
| Operating Environment | 14 to 122F (-10 to 50C), 0-95% RH non-condensing |
| Dimensions | 4.0 in H x 4.4 in W x 2.1 in D, plus 6.8 in probe |
Documentation
Related Products
Frequently Asked Questions
What CO2 range does the CT1D-A3X use?
This no-display unit is fixed at the factory-default 0-2000 ppm range. The selectable 0-5000 and 0-10000 ppm ranges require the LCD/menu (D-suffix) version.
Does the CT1D-A3X auto-calibrate?
Yes. The NDIR element uses selectable Automatic Baseline Correction (ABC) that tracks low ambient CO2 to offset long-term sensor drift. For continuously occupied spaces or greenhouses, Senva recommends the dual-channel option instead of disabling ABC.
Does the CT1D-A3X measure temperature?
No. The A-option is CO2 only. For combined CO2 and temperature, choose a B (active transmitter) or C/D/E/F/K (passive RTD/thermistor) configuration.
Is the CT1D-A3X made in the USA?
Yes. Senva manufactures the CT1D in Beaverton, Oregon, and the CT1D series is listed on Senva's 2026 Buy America / BABAA / TAA Commerce Declaration with domestic content exceeding 65%.
What is the warranty on the CT1D-A3X?
Senva backs the CT1D with an industry-leading 7-year limited warranty on the electronics; the NDIR sensing module carries a 3-year warranty.
Warranty
Senva backs the CT1D-A3X with an industry-leading 7-year limited warranty on the electronics. The NDIR CO2 sensing module carries a 3-year warranty. The field-replaceable CO2 element keeps total lifetime cost low across the sensor's 15+ year service life.
ZOT Supply is an authorized Senva distributor; your CT1D ships factory-fresh with the full Senva warranty. Warranty covers defects in materials and workmanship under normal use and service. Refer to Senva's published warranty terms for full conditions and exclusions.
- Sensor Type:
- Duct Mount
- CO2 Element:
- Yes
- Temperature Element:
- None
- Humidity Element:
- None
- VOC:
- No
- Display:
- No Display
- CO2 Range:
- 2000ppm Fixed
- Supported Protocols:
- None
- Country of Origin:
- USA
