Series 3868 Tell Tale Jr.™ Open Heater Detector

Indicates Open Loads

The Tell Tale Jr.™ Open Heater Detector is designed to indicate an open heater or other resistive load. Several models are available for various applications. The LED models light an LED when current is flowing in the circuit. If current stops flowing, the LED turns off. Solid state switch models provide either a logic output for DC applications or a triac output for AC applications. These models will satisfy those applications that need to send heater data to a PLC or computer having an appropriate power supply. They are provided with 4 foot leads. If the triac output model is used to drive an inductive load (relay coil, etc.) then the 3138-0412 snubber network is required. While the Tell Tale Jr.™ Detector is self-powered there is no power loss in the monitored load circuit when installed.

The Tell Tale Jr.™ Detector installs easily in new or existing systems. It consists of a specially designed doughnut shaped current transformer that is installed by passing one of the heater hookup wires through its center one or more times. Nylon tie wraps are included to anchor the detector to the wire. The detector can be installed on loads with ratings of 1 to 100 amperes. LED models on a 4 foot extension cable include a mounting bezel to facilitate mounting the LED on the front of a panel board. Cables may be extended up to 3,000 feet if necessary using 22 ga. copper wire.

Ambient temperature range for LED models is 0 to 70°C, logic output 0 to 60°C and triac output 0 to 40°C at 0.5A with de-rating to 0.35A at 60°C.

Models & Ordering

Shipping Information

All shipping times are dependent on product availability at time of shipment.

Although we make every effort to ensure a continuous supply of our products, occasional circumstances may force us to temporarily run out of a product, or have shipping delays. Should this occur, customers will be notified soon after placement of any orders for such products and, if applicable, items will be put on backorder. For orders requiring expedited shipment, our customer service team can be contacted to confirm product availability

COVID-19 Update: Due to high customer demand, lead time on some products may be up to two weeks. While this is a developing health situation, we are working continuously to take the necessary measures to ensure that the products you need are available with minimal interruption.

Model Description Usually Ships* Price Order
Ships: Less Than 1 Week
Price: $67.50
Open heater detector, triac output, no LED, 4 ft (1.2 m) cable. Less Than 1 Week* $67.50 Order
Ships: Less Than 1 Week
Price: $67.50
Open heater detector, logic output, no LED, 4 ft (1.2 m) cable. Less Than 1 Week* $67.50 Order
Ships: Less Than 1 Week
Price: $44.50
Open heater detector, external, red LED, 4 ft (1.2 m) cable, indication only. Less Than 1 Week* $44.50 Order


Red or green LED depending on model.
Logic: 0.25A @ 60 VDC max; Triac: 0.5A @ 120 VAC.
Operating Temperature:
Indication Only: 32 to 158°F (0 to 20°C); Logic: 32 to 140°F (0 to 60°C); Triac: 32 to 104°F (0 to 40°C).


  • Low Cost Current Indication
  • Easy Installation
  • Indicator or Switch Action
  • Draws No Power from Process
  • Compact Size
  • Isolated - No Direct Contact with Power Lines

Product Literature

Catalog Pages


Photo Downloads

You must be logged in to view this content.
Click here to login to your account.

Product Reviews

Only registered users can write reviews. Please Sign in or create an account