Series-681

Supported Applications

The Dwyer Series 681 Sanitary Pressure Transmitter is designed for sanitary installations according to 3A Standard #37-01. The series serves applications in food, dairy, beverage, and pharmaceutical processing. It supports liquid level control and monitoring within sanitary pipelines.

The unit features a fully sealed design intended to withstand high-pressure wash-down environments typical of Clean-in-Place (CIP) and Sterilize-in-Place (SIP) installations. The transmitter is insensitive to vibration, shock, EMI/RFI interference, and thermal shocks associated with these processes.

Operating Conditions & Performance

The Series 681 operates within a process temperature range of -40°F to 260°F (-40 to 125°C). The compensated ambient temperature range is specified as 20 to 180°F (-7 to 80°C), with humidity limits of 10 to 90% RH, non-condensing.

Performance specifications include an accuracy of ±20% FS (includes non-linearity, hysteresis and non-repeatability). The response time is documented as ≤ 10 ms. Thermal effects result in a zero and span shift of ±2.0% FS/100°F.

The transmitter utilizes a unique, no liquid fill diaphragm design. It provides a 4-20 mA, 2-wire output signal powered by 9-30 VDC, with a maximum loop resistance of 800 Ω. The unit weighs 8 oz (227 g).

Configuration Options

The series offers multiple measurement ranges to accommodate specific process requirements. Available pressure spans include:

• 681-02: 0 to 1 psi (Overpressure: 50 psi)
• 681-12: 0 to 2 psi (Overpressure: 100 psi)
• 681-42: 0 to 15 psi (Overpressure: 150 psi)
• 681-52: 0 to 30 psi (Overpressure: 150 psi)
• 681-62: 0 to 60 psi (Overpressure: 180 psi)

The process connection is a 2" or 1-1/2" sanitary clamp fitting male NPT. Wetted parts are constructed from 316L SS, compatible with liquids and gases. The electrical interface includes a 1/2" conduit fitting and strain relief with 15 ft (4.5 m) cable.

The transmitter features non-interactive zero and span adjustment capabilities of ±0.5 mA. Clamping effects on performance are documented as:

• ±0.15% FS for ranges up to 30 psi
• ±0.25% FS for ranges >30 psi

An optional NIST traceable calibration certificate (Order Code: NISTCAL-PT1) is available.

Key Product Differences

The Series 681 distinguishes itself through its sanitary clamp fitting design and no liquid fill diaphragm, which ensures negligible clamping effect on the output signal. The unit is factory calibrated and requires minimal field adjustment; however, if adjustments are made, zero and span screws with O-rings must be replaced to prevent moisture ingress.

Physical dimensions for the transmitter body include a diameter of 2.516 [64], height of 2.272 [58], and process connection height of 1.743 [44]. The design is completely watertight, utilizing sealed screws for adjustment access.