For critical infrastructure such as data centres, maintaining operational stability is paramount. This application required a high-accuracy, robust water level monitoring solution for an outdoor cooling tower, where environmental hazards like lightning strikes posed a significant threat to instrumentation. The solution involved a specialised submersible transmitter that combined precision measurement with a multi-layered approach to surge protection, ensuring reliable performance for the facility’s critical alarm system.
- Application Challenge: High-accuracy hydrostatic level measurement in a data centre cooling tower for a critical warning system.
- Environmental Constraint: The outdoor installation required robust protection against damage from electrical surges caused by lightning.
- Product Solution: An SLS-A series submersible level sensor with ≤±0.10% accuracy and an integrated Gas Discharge Tube for surge protection.
- Key Benefit: The combination of high-precision measurement, active temperature compensation, and a comprehensive lightning protection strategy ensures exceptional reliability and system uptime.
An engineering projects manager overseeing the installation of a critical warning system for a data centre required a highly reliable method for monitoring the water level in an outdoor cooling tower. The application presented a distinct set of challenges, demanding not only high precision but also extreme resilience against environmental hazards. The measurements were essential for triggering alarms to maintain operational stability, as incorrect water levels in a cooling tower can compromise the efficiency of the entire data centre’s cooling infrastructure, risking costly downtime.
The primary requirement was for a hydrostatic level sensor capable of measuring a relatively shallow depth of up to 1 metre of water. Due to its role in a critical warning system, the sensor needed to provide the highest possible accuracy. Furthermore, the outdoor installation meant the entire measurement system was highly susceptible to damage from electrical surges caused by nearby or direct lightning strikes, a risk that needed to be explicitly mitigated. The solution also required a standard 4-20mA analogue output for seamless integration with the facility’s existing monitoring and control systems, along with a cable of sufficient length to run from the sensor’s position in the cooling tower basin to a local junction box.
The proposed solution centred on the SLS-A series submersible level transmitter. This instrument was selected for its ability to directly address all of the application’s stringent requirements. To meet the demand for precision, a version with a measurement accuracy of better than ≤±0.10% of full scale was specified. This high level of performance is achieved through the use of an advanced piezoresistive silicon sensing element paired with an onboard 16-bit microprocessor, which provides active linearisation and temperature compensation. This is particularly beneficial in an outdoor installation where ambient temperature fluctuations could otherwise impact measurement stability; the sensor’s low thermal zero and span coefficient of just ±0.015%FS/∘C ensures consistent readings regardless of the weather conditions.
The sensor’s construction is designed for long-term immersion and environmental resilience. The robust 316 stainless steel housing and a high-integrity over moulded cable assembly provide durable protection against the fresh water medium. A key feature for this type of hydrostatic measurement is the vented polyurethane (PUR) cable. This cable incorporates a micro-tube that runs its entire length, providing the sensor’s diaphragm with a real-time atmospheric pressure reference. This gauge reference is critical for ensuring that the sensor only measures the hydrostatic pressure from the water column, automatically compensating for any changes in barometric pressure and thus providing a true water level measurement. To address the significant risk of lightning, a multi-layered protection strategy was implemented. The SLS-A sensor itself features an integral Gas Discharge Tube (GDS) for lightning protection, providing a first line of defence against transient over-voltages. To further safeguard the entire measurement loop, an additional heavy-duty surge protection device was recommended for installation within the customer’s junction box, ensuring the integrity of the 4-20mA signal and protecting the connected control system hardware.
SLS-A SLS-A Lightning Protected Submersible Level Transmitter
- Part No: SLS-A-DC-A005-BV-0100G-00
- Level Range: 0 – 1mWG
- Pressure Datum: Gauge
- Output Type: 4-20mA / 2-wire
- Accuracy Class: <±0.10 %
- Lightning Protection: Integral GDS (gas discharge tube)
- Cable material: PUR
- Cable Length: 5m
- Housing material: 316L Stainless Steel
- Process Connection: G1/4 male DIN3852 with removable nose cone
- Seal Material: Viton
- Special Options: None
ESP30D Data & Signal Protector
- Part No: ESP30D
- Mounting: DIN Rail