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EnglishWhat Are Gems Pressure Switches, Flow Switches, and Level Switches Used For?
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Gems pressure switches, flow switches, and level switches are industrial automation components used to detect a physical condition and trigger a control action—such as starting a pump, closing a valve, or sending an alarm. They belong to the Gems product family within the Danaher/Sensata sensing and control group, which also includes Setra precision pressure transducers. If your task is to monitor or interlock pressure, flow, or liquid level in a machine or process line, these are the relevant device categories. The sections below explain what each type does, how it differs from a continuous-output sensor, and what to confirm before selecting a model.
The Gems product family at a glance
According to the supplier page, Gems and Setra are brands under the Danaher sensing and control group, which has more than sixty years of experience in process and factory automation. The product range covers:
- Pressure transducers and transmitters (including Setra precision pressure transducers)
- Pressure switches
- Flow switches and flow sensors
- Level switches and level sensors
- Temperature controllers, rotary encoders, counters, and related instruments
The same source lists Gems, Setra, Sensors, Hengstler, WEST Instruments, and PMA as brands in this group. For a buyer, this matters because pressure, flow, and level devices from one family can often share installation practices and be specified together for a single skid or panel.
What each switch type is used for
Pressure switches
A pressure switch closes or opens an electrical contact when pressure crosses a set threshold. Typical uses:
- Turning a pump on or off to maintain pressure in a tank or line
- Tripping an alarm or shutdown when pressure falls too low or rises too high
- Interlocking a compressor or hydraulic circuit
The key distinction from a pressure transducer: a switch gives a discrete on/off signal, while a transducer gives a continuous analog output proportional to pressure. If you need to display or log the actual pressure value, choose a transducer or transmitter. If you only need a trip point, a switch is usually simpler and cheaper to wire.
Flow switches
A flow switch detects whether flow is present, absent, or above a minimum rate, and outputs a contact signal. Common applications:
- Proving that coolant or lubricant is circulating before allowing a machine to run
- Protecting a pump from running dry
- Alarm on loss of flow in a process line
A flow sensor, by contrast, measures the actual flow rate and provides a continuous signal. Use a switch for go/no-go protection; use a sensor when you need to totalize, control, or record flow.
Level switches
A level switch detects a liquid level at a specific point—high, low, or both—and outputs a contact. Uses include:
- High-level alarm to prevent tank overflow
- Low-level cutoff to protect a pump
- Automatic fill or drain control
The supplier page also lists related options such as photoelectric level switches and ultrasonic level switches, which suit different media and mounting conditions. Point-level switches are for a single threshold; if you need continuous level measurement, a level transmitter is the appropriate category.
Switch vs. continuous sensor: a quick comparison
| Device | Output | Typical job |
|---|---|---|
| Pressure switch | Discrete contact | Trip, alarm, pump control at a set point |
| Pressure transducer/transmitter | Continuous analog | Measure, display, or log pressure |
| Flow switch | Discrete contact | Prove flow, dry-run protection |
| Flow sensor | Continuous analog/pulse | Measure or totalize flow rate |
| Level switch | Discrete contact | High/low alarm, fill/drain control |
| Level transmitter | Continuous analog | Continuous level measurement |
What to confirm before choosing a model
Selection should start from the application, not the model number. Confirm these points first:
- Medium and compatibility — what fluid or gas contacts the wetted parts, and does the material suit it?
- Range or set point — the pressure, flow, or level threshold the device must respond to.
- Output signal — discrete contact for a switch, or analog/pulse for a sensor.
- Process connection — thread type and size, and how the device mounts.
- Electrical and environmental conditions — supply, contact rating, and the ambient conditions at the installation point.
Once these are fixed, match them against the specific Gems or Setra datasheet. The supplier page presents the product categories but does not list individual model specifications, so model-level parameters should be confirmed from the manufacturer's datasheet or by contacting the distributor directly.
Where to get product and contact information
The supplier, Beijing Tide Science and Technology Co., Ltd. (北京中科泰德科技有限公司), lists its sensor division as focused on promoting and supporting Setra, Gems, and Sensata pressure sensors/transmitters, pressure switches, flow switches, flow sensors, and level sensors for industrial automation. The page provides phone numbers (010-88239428, 010-88239430) and a fax number (010-68163448) for inquiries. Pricing is not stated on the page, so cost and availability need to be confirmed through direct contact.