Capturing the rising limb of a storm event and having the ability to collect water samples from industrial dischargers with intermittent flows can be challenging for agencies tasked with these responsibilities. This article details how a small, inexpensive tool available from Teledyne ISCO can aid both of these applications and more.

The model 1640 Liquid Level Actuator is a device used in conjunction with an ISCO sampler to begin a sampling routine when water/wastewater is present or reaches a pre-determined height.

The liquid level actuator consists of a small control box assembly connected to the end of a 22 ft. coaxial cable terminating in a probe. When water contacts the probe end or ring, it completes an electrical connection that the 1640 translates into an enable condition on the sampler. The control box has a switch to toggle between two settings: Latch Mode and Toggle/Reset Mode. The device also includes a compatible connector to plug-in to the 6-pin Flow Meter port on any Teledyne ISCO sampler controller. The sampler connector provides power to the actuator and receives the output signal from the actuator.

 If your goal is to simply enable the automatic sampler when liquid is detected, such as in a normally dry storm-water outfall, you can lay the sensor tip in the bottom of a channel. A recommended method is to position the 1640 probe tip off of the channel bottom so that at a minimum it is the height of the sampler strainer. This insures that when the sampler is enabled there is adequate liquid level to cover the strainer preventing a missed sample and a sampler error from occurring. If the channel typically has a base flow you can insert a stake/pole or fashion a mount to hold the probe tip at a specific height above the base flow surface so that when there is an event, the water rises, contacts the sensor and enables the sampler to begin running its program.

The 1640 can be set up to operate in either one of two available modes, Latch or Toggle/Reset. In Latch mode the 1640 maintains the sampler enable condition even if the water level drops back down below the level of the 1640 probe. In other words, once enabled, the sampler will continue running its program regardless of the water level. In Toggle/Reset mode the sampler is only enabled as long as water is contacting the sensor. As soon as the water drops below the sensor the sampler is inhibited from running its program until water again contacts the sensor tip/ring.

The 1640 Liquid Level Actuator, with the appropriate cables, can also be used in conjunction with a flow meter for flow-paced sampling. With this combination, the sampler is inhibited from running its flow-paced program, even while receiving input from the flow meter, until the water contacts the 1640 sensor. This setup may be important to a storm-water manager who desires to collect flow paced samples during a storm event only, not during base flows.

When used with the Teledyne ISCO GLS sampler in Toggle/Reset mode it is necessary to put the GLS in a “repeatable enable” condition. To perform this setup, from the main screen of the GLS, type the characters 1 6 4 0 <Enter>. You will not see any of these characters appear on the GLS LCD while typing; however, as soon as you press <Enter> you will be prompted with a single menu “Repeatable Enable” Yes or No, highlight “Yes, press <Enter> and your GLS sampler program will now only be enabled when water is contacting the probe.

The model 1640 Liquid Level Actuator Attached to the side of an ISCO Sampler

The 1640 Liquid Level Actuator is an inexpensive and simply tool to help water resource managers use their automatic samplers more effectively. The 1640 along with other instruments and samplers can be obtained by contacting Frontier Precision.


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