OTC Transmitters


Battery-Powered Self-Contained Level Sensing Solutions

SM-RL1 | SM-RL1-T | SM-RL2 | SM-RL2-T


  • Monitor product, interface & temperature using a single Resistive Level Sensor
  • Up to a 10-year battery life
  • ± 1/8” accuracy on 1/4“ sensor* (T option)
    *API 18.2-compliant
  • ± 1/4” accuracy on 1/2“ sensor
  • Flex (PTFE) or rigid (316 SS) sensor option
  • Multiple liquid compatibility
  • Sensor only requires a one-time calibration
  • Installs in minutes: Quick Connect  eliminates sensor wiring error and hassle
  • Highly resistant to H2S damage, scaling, and paraffin buildup (Limited lifetime warranty, please contact your OleumTech representative
    for details)
  • Supports Over-the-Air (OTA) functionality for updating the device configuration/calibration
  • Self-contained, rugged design, IP66
  • Sensor supports a wide temperature range
  • -40 ˚C to 120 ˚C / -40 ˚F to 248 ˚F
  • 900 MHz range: Up to 1.4 Miles / 2.3 km with Clear Line of Sight
  • Secure AES encryption
  • Class I, Division 1 (Zone 0), Intrinsically Safe
  • US Patent #6,967,589 & #8,763,455 B1

Accurate Level Sensing Solution

OleumTech® designed the OTC Wireless Resistive Level Transmitter to connect and power its flagship line of Resistive Tanks Level Sensors for enabling remote collection of critical tank level data. The self-contained, battery-powered transmitter and sensor combination delivers exceptional performance, reliability, and accuracy, and is made to thrive under extreme outdoor conditions.

All OleumTech Resistive Level Sensors offer industry-leading 3-in-1 monitoring capabilities of product (oil), interface (water), and temperature from a single instrument. Ordering the SM-RL2 and SM-RL2-T transmitter option provides two additional discrete inputs, giving you a total of 5-in-1 monitoring capabilities.

The SM-RL1-T and SM-RL2-T options are compatible with the 1/4” resolution sensors providing API 18.2 compliance for handling custody transfer applications while the SM-RL1 and SM-RL2 work with 1/2” resolution sensors. A single, replaceable battery pack powers both the transmitter and sensor and can last up to 10 years.

Reliable, Scalable, and Safe

The field-proven wireless level transmitter communicates with an assigned wireless gateway within the OTC Wireless Sensor and I/O Network, creating a highly scalable network, accommodating virtually any I/O requirement.

OleumTech wireless level transmitters and sensors are certified for use in Class I, Division 1 (Zone 0) hazardous locations. They are intrinsically safe, designed not to cause a spark and can be serviced without being removed from a process.

This product is also available with a local display.

This product is also available in a hardwired version.


The Resistive Level Sensors are ideal for use as oil level sensors, water level sensors for storage tanks that contain either or both liquid densities. These level instruments are widely used in oil production tank batteries, condensate tanks, water treatment centers, petrochemical and chemical-making plants, wastewater handling and storage facilities, refineries, and power generating plants.


Radio Band∙ ISM Band (License-Free)
900 MHz∙ FHSS, FSK, AES Encryption 256-bit (900 MHz)
Bit Rate∙ 900 MHz: 9600 bps / 115.2 kbps
Output Power (Max)∙ 900 MHz: 10 mW
Receiving Sensitivity∙ 900 MHz: -110 dBm @ 9600 bps, -100 dBm @ 115.2 kbps
RF Range∙ 900 MHz: Up to 7500 Feet / 1.4 Miles / 2.3 km with Clear Line of Sight
Device Functionality∙ OTC Wireless Transmitter with Support for Resistive Level Sensors
Model Configuration∙ SM-RL1: 1/2" Resolution, Product, Interface and Temperature (6-pin Quick Connect)
∙ SM-RL2: 1/2" Resolution, 2 Discrete Inputs + Product, Interface and Temperature (6-pin Quick Connect)
∙ SM-RL1-T: 1/4" Resolution, Product, Interface and Temperature (8-pin Quick Connect)
∙ SM-RL2-T: 1/4" Resolution, 2 Discrete Inputs + Product, Interface and Temperature (8-pin Quick Connect)
Embedded Controller∙ Ultra-Low Power RISC Microcontroller with Internal FLASH (Field Upgradeable)
Configuration∙ Standard RS232 Serial / BreeZ® Software for PC (v5.5 or higher for 1/4" Resolution Models)
Resolution∙ Resolution Depends on Sensor Type: 1/4" (6.4 mm) or 1/2" (12.7 mm)
Accuracy∙ 1/4" Resolution Sensor: ±1/8" (2/16") Accuracy; 1/2" Resolution Sensor: ±1/4" Accuracy
∙ 6.4 mm Resolution Sensor: ±3.2 mm Accuracy; 12.7 mm Resolution Sensor: ±6.4 mm Accuracy
2 Discrete Inputs∙ Dry Contact, NPN (Sink), Debounce Filter 20 - 2000 ms (Available on SM-RL2/SM-RL2-T)
Power Source∙ Self-Contained, Internal 3.6 Vdc Lithium Battery
Internal Battery Life∙ Up to 10 Years, Based on User Defined Reporting Intervals
Device Diagnostics∙ Health Tags: Battery Voltage, Received Signal Strength Indication (RSSI), RF Refresh, RF Timeout, Error Codes
Dimensions, SM-RL1/SM-RL1-T∙ RL1: 5" (W) x 7.9" (H) x 4.4" (D) / 127 mm (W) x 201 mm (H) x 112 mm (D)
Dimensions, SM-RL2/SM-RL2-T∙ RL2: 5" (W) x 12.9" (H) x 4.4" (D) / 127 mm (W) x 328 mm (H) x 112 mm (D)
Package Dimensions∙ 10.25" (W) x 14" (H) x 6.5" (D) / 260mm (W) x 356mm (H) x 165mm (D)
Package Weight∙ SM-RL1/SM-RL1-T: ~5.5 lbs / 2.5 kg | SM-RL2/SM-RL2-T: 7 lbs / 3.2 kg
Connection Fitting∙ Quick Connect Adapter to Sensor - No Wiring Required, RL2: 2 3/4" NPT Female Ports (Both Plugged)
Enclosure Casing Material∙ Type 4X Aluminum; IP66
EMC/EMI∙ FCC Part 15 (USA), IC ICES-003 (Canada), ACMA (Australia)
∙ AS/NZS CISPR 32 (Australia), EN55032 & EN55024 (EU)
Safety∙ Class I, Division 1, Groups A, B, C, D T3C; Ex ia IIC T3
∙ Class I, Zone 0; AEx ia IIC T3
∙ ATEX: Sira 13ATEX2142X; Ex ia IIC T3 Ga; II 1 G
∙ IECEx: SIR 13.0054X; Ex ia IIC T3 Ga
1/2" Sensor Kits w/Float(s)1/2" TGxxxFxx (Flex) and ZGxxxFxx (Rigid) Works with SM-RL1 and SM-RL2
1/4" Sensor Kits w/Float(s)1/4" THxxxFxx (Flex) and ZHxxxFxx (Rigid) Works with SM-RL1-T and SM-RL2-T
Operating Conditions∙ Ambient Temperature (Class I, Division 1 / Zone 0): -40 °C to 70 °C (-40 °F to 158 °F)
∙ Ambient Temperature (Non-Hazardous Applications): -40 °C to 80 °C (-40 °F to 176 °F)
∙ Humidity: 0 to 99 %, Non-Condensing
Warranty∙ 2-Year Parts and Labor
Country of Origin∙ USA
SENSORRIGID: 316 Stainless Steel "SS"FLEX: Polytetrafluoroethylene "PTFE"​
TypeExtremely Reliable and Accurate Resistive Reed Switch Technology
Measurement Capabilities (3-in-1)Product, Interface, and Temperature
Lengths Offered in US Units2 to 26 ft Length in 1 ft Increments8 to 38 ft Length in 1 ft Increments
Lengths Offered in Metric0.61 to 7.9 m in 0.31 m increments2.44 to 11.58 m in 0.31 m increments
Resolution and AccuracyOption 1: 1/2" (12.7 mm) Resolution with ±1/4" ( ±6.4 mm) Accuracy (6-pin Quick Connect)
Option 2: 1/4" (6.4 mm) Resolution with ±1/8" (±3.2 mm) Accuracy (8-pin Quick Connect)
Sensor to Interface Mating Connection (No Wiring Solution)316 SS Quick Connect: 6-pin Connection for 1/2" Resolution, 8-pin Connection for 1/4" Resolution
Tank Mating Connection (Adjustable Compression Fitting)3/4" NPT Male1" NPT Male
Temperature Accuracy±1 °C
Anchor Weight DiameterN/A2.4" / 60.3 mm
Height of Anchor WeightN/A8 to 19 ft Sensor: 5"
20 - 28 ft Sensor: 6.75" / 29 - 38 ft Sensor: 8"
Coiled DiameterN/A20" (50.8 cm) Coiled Diameter
Minimum Measurement from Bottom (Deadband)2" (50.8 mm) from BottomFrom Top of Anchor Weight
Pressure RatingFloat DependentFloat Dependent
Sensor Only without Float(s)569 PSI (39 Bar)142 PSI (9.8 Bar)
Sensor w/ 316 SS Float - Small*440 PSI (30 Bar)N/A
Sensor w/ 316 SS Float - Large356 PSI (24.5 Bar)142 PSI (9.8 Bar)
Sensor w/ Polyvinylidene Fluoride (PVDF) Float72.5 PSI (5 Bar)72.5 PSI (5 Bar)
Float Options:
*316 Stainless Steel - Small, (Fx0)Compatible Only with Rigid Sensor Length up to 7 ft
Product: 0.64 SG, Interface: 0.96 SG, ID 0.72" (18.3 mm), OD 2.05" (52.1 mm), H 2.71” (68.83 mm)
316 Stainless Steel - Large, (Fx1)Product: 0.62 SG, Interface: 0.95 SG, ID 1.12" (28.5 +/-0.5 mm), OD 2.83" (72 mm), H 4.65” (118 +/-1 mm)
Polyvinylidene Fluoride (PVDF), (Fx3)Product: 0.64 SG, Interface: 0.96 SG, ID 1.18" (30 +0.3/-0 mm), OD 2.83" (72 +/-0.25 mm), H 1.77” (45 +/-1 mm)
Operating Temp. Sensing Area-40 °C to 120 °C (-40 °F to 248 °F)
CertificationsClass I, Division 1, Groups C, D T4; Ex ia IIB T4 Ga; Class I, Zone 0, AEx ia IIB T4 Ga
ATEX: Sira 16ATEX2229X; Ex ia IIB T4 Ga
IECEx: SIR 16.0079X; Ex ia IIB T4 Ga
Device CompatibilityOleumTech WT, SM, and H Series Resistive Level Transmitters
PowerThe Sensor is Powered by the Transmitter
Kit Ordering #: 1/2" Resolution with Float(s)ZGxxxFxxTGxxxFxx
Kit Ordering #: 1/4" Resolution with Float(s)ZHxxxFxxTHxxxFxx
Transmitters∙ SM5000-RL1 / SM5000-RL1-T / SM5000-RL2 / SM5000-RL2-T
Level Sensor Kits∙ 1/2" Resolution Sensor Kits: TGxxxFxx (Flex) and ZGxxxFxx (Rigid) (xxx = Length in Inches, Fxx = Float Configuration)
∙ 1/4" Resolution Sensor Kits: THxxxFxx (Flex) and ZHxxxFxx (Rigid) (xxx = Length in Inches, Fxx = Float Configuration)
Wirelessly Connects To∙ OTC Wireless Gateway
Configuration Cable∙ SX1000-CC2, 20-ft All-in-One Configuration Cable
Replacement Battery∙ Use OleumTech SX1000-BP3 Only