Sekonic ST-50A Digital Temperature and Humidity Chart Recorder
The Sekonic ST-50A is being phased out. Contact Seacom to confirm availability before ordering a recorder or specifying one for a new installation. Existing users can use this page to identify specifications, consumables and suitable alternatives.
The ST-50A displays temperature and relative humidity electronically and records both on a continuous paper chart. It is designed for indoor environmental recording in laboratories, storage rooms, production areas, museums and similar locations where a visible record is useful.
Key Features
- Simultaneous temperature and humidity display and paper recording.
- Electronic sensing with optional extension cables for remote sensor placement.
- Z-fold chart paper with separate temperature and humidity traces.
- Battery operation or a suitable external DC supply.
- Desktop or wall-mounted installation.
The ST-50A does not provide the ST-50M's SD-card recording function. Choose an electronic data logger or monitoring system if downloadable records are required.
Recommended Alternatives to the ST-50A
These are functional alternatives, not direct replacements with identical features or interchangeable accessories. If you need both an on-site paper trace and electronic records, tell us before selecting a replacement.
| Alternative | Recording method | When to consider it | Main difference from ST-50A |
|---|
| Sato Sigma II NSII-Q |
Temperature and humidity on a rotating paper chart |
Routine visual checks and paper filing |
Rotating drum rather than folded chart paper; no digital display or remote electronic probe. |
| Sato SK-L754 |
Electronic temperature and humidity records, with PC and microSD data transfer |
Local recording, trend analysis and electronic record storage |
No built-in chart printer; requires a compatible SK-L754 probe. |
| Vaisala RFL100 + AP10 with viewLinc |
Networked monitoring, historical records and configurable alarms |
Multiple rooms, warehouses, laboratories and controlled environments |
Requires a configured monitoring system; no built-in paper chart mechanism. |
For Paper Records: Sato Sigma II NSII-Q
The Sigma II is a practical alternative when staff need to inspect and retain a physical temperature and humidity chart. It uses separate pens and a rotating drum, so its recording process differs from the ST-50A's folded chart paper.
- 7210-00: temperature scale −15 to 40°C and humidity scale 0 to 100% RH.
- 7211-00: temperature scale −10 to 50°C and humidity scale 0 to 100% RH.
- Select the correct chart for the recorder model and recording period.
- ST-50A charts, pens and remote sensors are not interchangeable with Sigma II accessories.
View Sato Sigma II thermohygrographs.
For Electronic Records: Sato SK-L754
The SK-L754 records temperature and humidity electronically, with capacity for 16,000 data records. Data can be transferred to a PC or copied to a microSD card, and the dedicated software supports graphing and CSV export.
- SK-L754-1 plug-in probe: −10 to 60°C and 5 to 95% RH.
- SK-L754-2 cabled probe: −20 to 80°C and 5 to 95% RH.
- A compatible probe must be selected separately; check the logger body's ambient limits as well as the probe range.
- The SK-L751 is a temperature-only logger. Choose SK-L754 when humidity must also be recorded.
The SK-L754 replaces the paper-recording workflow with electronic logging. It has no built-in chart printer. Select a recording interval and download schedule suitable for your required retention period.
View Sato SK-L750 Series data loggers.
For Centralised Monitoring: Vaisala viewLinc
For monitoring across several locations, consider Vaisala RFL100 data loggers with suitable humidity and temperature probes, AP10 access points and viewLinc software. The system combines historical records with configurable alarms and reporting.
This is a system upgrade for applications such as pharmaceutical storage, laboratories and controlled rooms. Seacom can help review measurement locations, network coverage, alarm requirements and calibration needs. The logger, probes, access point and software must be specified together.
View Vaisala RFL100, AP10 and viewLinc monitoring options.
ST-50A Specifications for Existing Installations
The following specifications refer to the ST-50A. Replacement instruments have their own ranges, accuracy specifications and installation requirements.
| Specification | ST-50A reference |
|---|
| Measurements |
Temperature and relative humidity |
| Standard measurement conditions |
−20 to 50°C; 20 to 90% RH, non-condensing |
| With sensor extension cable |
−20 to 80°C; 0 to 100% RH, non-condensing; recorder body must remain within its own operating limits |
| Temperature accuracy |
±1.0°C at 0 to 50°C |
| Humidity accuracy |
±3% RH at 25°C; guaranteed humidity accuracy range 10 to 90% RH |
| Display resolution |
0.1°C and 0.1% RH |
| Chart |
Z-fold paper, 113 mm wide × 12 m long; 100 mm working recording width |
| Recording method |
Paper chart; no ST-50M-style SD-card recorder |
| Power |
Four LR20 1.5 V batteries; 9 V DC, 500 mA adapter input |
| Dimensions and weight |
300 W × 245 H × 105 D mm; approximately 2.1 kg without batteries |
| Sensor types |
Semiconductor temperature sensor and capacitive humidity sensor |
| Calibration adjustment |
Temperature: one point; humidity: one or two points |
| Mounting |
Desktop or wall mounting |
The wider remote-sensor measuring range does not extend the recorder body's permitted ambient range. Keep the recorder within −20 to 50°C and 20 to 90% RH without condensation.
ST-50A Chart Paper, Pens and Accessories
The references below are retained from the existing product listing. Confirm the complete part number, pack quantity, compatibility and supply availability before ordering.
| Item | Legacy reference | Details |
|---|
| Standard chart paper |
HE12 / HE0140010 / HEGA |
Original listing: 5 pieces per set |
| Clean chart paper |
HE11 |
Original listing: 5 pieces per set |
| Cartridge pens |
HE13 / HEFA15330 / HEFA |
Original listing: 2 red and 2 blue pens per set |
| Sensor extension cable |
HE04 |
5 m |
| Sensor extension cable |
HE05 |
20 m |
| Sensor extension cable |
HE06 |
50 m |
| External control output unit |
HE09 |
Original listing: one common output |
See chart paper and recording consumables and recording pens, ink and ribbons for related enquiries.
ST-50A or ST-50M: Which Model Do You Have?
Check the model label before requesting parts or a replacement. The ST-50A is the paper-chart model; the discontinued ST-50M added SD-card recording and time printing. Similar appearance does not establish identical functions or accessory compatibility.
View ST-50M legacy information and alternatives.
Choosing an ST-50A Alternative
- Paper record: confirm whether a rotating drum chart is acceptable instead of a continuous folded chart.
- Sensor position: tell us if the sensor must be placed away from the recorder. A traditional thermohygrograph does not reproduce the ST-50A's remote electronic sensor arrangement.
- Measurement conditions: provide the required temperature and humidity range, accuracy and calibration requirements.
- Records and alarms: specify whether you need local paper records, downloadable files or a networked system with notifications.
- Existing accessories: include chart, pen and cable references; do not assume they can be reused with another recorder.
Need Help with an ST-50A Recorder?
Contact Seacom Process Instruments Sdn Bhd with your model number, application, measuring range and preferred recording method. For consumables or replacement advice, include photographs of the recorder label and the existing chart, pen or sensor connection.
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ST50 Catalogue
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