The STM94442A is a stationary tank-level monitor. That receives signals from compatible tank sensors and displays the measured level on its built-in LCD.
Separate high and low level thresholds can be programmed for each tank. When a level moves outside the set range, the matching Form C relay can trigger an external alarm, warning light, or control system.
The monitor also provides 0–5 VDC analog outputs and RS-232 communication for integration. Along with compatible PLCs, RTUs, computers and site-monitoring systems. Optional 4–20 mA outputs and a wireless link between the tank sensor and monitor are also available.
Key STM94442A features
- Monitors two stationary tanks with one unit
- Two-line, 16-character LCD
- Separate tank-level indication for each channel
- Field-programmable high and low set points
- Five-button parameter interface
- Form C dry-contact alarm relay for each channel
- 0–5 VDC analog output for each channel
- Optional 4–20 mA output for each channel
- RS-232 interface for programming and retrieving level data
- Compatible with PLCs, RTUs and external monitoring equipment
- Optional wireless connection between the monitor and tank sensor
- Compatible with Rochester Hall-effect LPG gauge sensors
- Accepts compatible 4–20 mA sensor signals
- Weatherproof enclosure for indoor or outdoor installation
- Operating temperature from approximately –29°C to 60°C
LPG and propane tank-level monitoring
The STM94442A provides an effective way to monitor stationary LPG and propane tanks fitted with compatible level sensors.
Tank levels are shown locally on the LCD. Therefore, allowing maintenance personnel and site operators to check the available LPG without inspecting the tank gauge directly. Programmable high and low thresholds can also be used to activate external alarms or connected control equipment.
The monitor is compatible with suitable Rochester Hall-effect gauge senders commonly used in LPG tank applications.
Backup generator fuel monitoring
Standby generators can only provide emergency power when sufficient fuel is available. The STM94442A can form part of a generator fuel tank monitoring system for stationary diesel or LPG tanks.
The monitor allows operators to:
- View the current tank level locally
- Establish high and low fuel thresholds
- Activate an external alarm when fuel falls below the selected level
- Send tank-level information to a PLC, RTU or computer
- Monitor two generator fuel tanks from one unit
- Incorporate fuel-level data into a wider site-control system
These capabilities make it suitable for backup generators at telecommunications sites, utilities, industrial facilities and other critical infrastructure.
Telecommunications and remote-site fuel monitoring
LevelCon developed the STM94442A for applications requiring dependable fuel-level monitoring at telecommunications, cellular, radio and cable tower sites.
According to LevelCon, the STM94442A has been used for more than 25 years. In addition, it is installed at over 100,000 communications sites across the United States. Its established field history makes it particularly relevant to remote facilities. Especially on those that depend on diesel or LPG generators during mains-power interruptions.
Potential applications include:
- Cellular and radio towers
- Telecommunications facilities
- Broadcast transmission sites
- Emergency communications infrastructure
- Utility sites and substations
- Water and wastewater pumping stations
- Remote industrial facilities
- Backup power installations
- Data centres and critical facilities
PLC, RTU and SCADA integration
The STM94442A can provide tank-level and alarm information to compatible external control and monitoring equipment.
Each channel provides a 0–5 VDC analog output, with optional 4–20 mA outputs available. The RS-232 interface can also transmit live tank-level and set-point information to a connected computer or RTU.
Integration options include:
- PLC tank-level monitoring
- RTU fuel-level monitoring
- SCADA and site-control systems
- Building management systems
- External alarm panels
- Computers used for monitoring or data logging
Remote access, notifications and historical data logging require connection to appropriate external communications or monitoring equipment. These functions are not provided by the standard STM94442A alone.
Compatible liquids and sensors
The STM94442A measures the signal received from a compatible level sensor. Rather than contacting or measuring the stored liquid directly.
Depending on the selected sensor and installation, it may be used for:
- LPG
- Propane
- Diesel
- Fuel oil
- Ammonia
- Other compatible industrial liquids
Sensor suitability, materials compatibility and hazardous-area requirements must be assessed for each application. Additional approved barriers or equipment may be necessary when monitoring petrol, flammable liquids or tanks installed in hazardous locations.
Metromatics can help identify an appropriate monitoring configuration for your tank, sensor requirements.
Technical specifications
| Specification | STM94442A |
|---|---|
| Product type | Two-channel stationary tank-level monitor |
| Number of tanks | Up to two |
| Display | Two-line, 16-character LCD |
| User controls | Five parameter-setting buttons |
| Level set points | Field-programmable high and low set points |
| Sensor inputs | Two analog sensor inputs |
| Standard analog outputs | 0–5 VDC per channel |
| Optional output | 4–20 mA per channel |
| Alarm outputs | Form C dry-contact relay per channel |
| Communications | RS-232 for programming and level-data retrieval |
| Sensor compatibility | Rochester Hall-effect senders and compatible 4–20 mA sensors |
| Wireless option | Optional wireless link between the monitor and tank sensor |
| Enclosure | Weatherproof |
| Dimensions | Approximately 114 × 165 × 76 mm |
| Operating temperature | Approximately –29°C to 60°C |
| Monitor input power | 10–24 VDC |
| Country of origin | More than 50% assembled in the USA |
Specifications and available options should be confirmed for the required configuration before ordering.
Benefits of stationary tank-level monitoring
Installing a local tank-level monitor can help organisations:
- Identify low generator-fuel levels before an outage
- Reduce unnecessary manual tank inspections
- Provide tank-level visibility at a more convenient location
- Activate external alarms at selected high or low levels
- Connect existing tanks to PLC or RTU systems
- Monitor two tanks using one controller
- Improve planning for LPG or diesel replenishment
- Detect unexpected changes in tank level for further investigation
Frequently asked questions
Can the STM94442A monitor two tanks?
Yes. The STM94442A has two tank-monitoring channels. Therefore, allowing one unit to display and monitor the level of two compatible stationary tanks.
Does the STM94442A include a tank-level sensor?
The required sensor depends on the tank, liquid and existing gauge arrangement. The STM94442A supports compatible sensors, including appropriate Rochester Hall-effect LPG gauge senders and 4–20 mA devices. Confirm the required sensor configuration with Metromatics.
Can it monitor a diesel generator fuel tank?
Yes. When connected to an appropriate sensor. Firstly, the STM94442A can monitor a stationary diesel tank used to supply a standby or backup generator.
Can the monitor activate a low-fuel alarm?
Yes. High and low level set points can be programmed for each channel. A Form C relay output can activate compatible external alarm or control equipment. Especially, when the tank level moves outside the selected range.
Can the STM94442A connect to a PLC or RTU?
Yes. The monitor provides 0–5 VDC analog outputs and RS-232 communication. Optional 4–20 mA outputs are also available for compatible industrial monitoring and control systems.
Does it provide remote tank monitoring?
The STM94442A can supply tank-level information to an external PLC, RTU or computer. Remote access and notifications require suitable external communications and monitoring equipment.
Is wireless tank monitoring available?
An optional wireless link is available between the tank sensor and the monitor. This can reduce the need to run a physical cable between those two components. It should not be confused with standalone mobile or cloud connectivity.
Can it be used with liquids other than LPG?
Yes, provided the selected level sensor and installation are suitable for the liquid. Potential applications include propane, diesel, fuel oil and ammonia tanks. Hazardous liquids and locations may require additional equipment.
Enquire about the STM94442A
Finally, Metromatics supplies LevelCon LPG tank monitoring and generator fuel monitoring equipment in Australia and New Zealand. Contact us now.
A wireless version is also available for applications needing cable-free communication between the tank sensor and monitoring unit.
