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Product details
About this part
The Halstrup Walcher REG 21 Differential Pressure Controller is made by Halstrup Walcher and identified by manufacturer part number REG 21.
This listing is for the exact part number stated above. Compare the part number, condition and photos with your equipment before ordering.
Condition
This item is listed as Used. Previously used. See condition notes and photos.
The photos are part of the description — check them for labels, connectors, markings and any visible wear.
What's included
1 × Halstrup Walcher REG 21 Differential Pressure Controller.
Only the items listed here or clearly shown in the photos are included. Cables, manuals, mounting hardware and accessories are not included unless stated.
Identification & compatibility
Check the manufacturer (Halstrup Walcher), the part number (REG 21) and the photos against your equipment. If you are not sure this is the right part, contact us before you order.
Price match
Found an identical item for less at a fixed price elsewhere? Contact us before you buy with the details, and we will review it.
Important information
Product information is based on what is available for this specific item. Where specifications or compatibility are critical to your application, confirm them before purchase.
- Brand
- Halstrup Walcher
- Part number
- REG 21
- Model
- REG 21
- Country of Origin
- Germany
- Manufacturer
- halstrup-walcher GmbH, Germany
- Label line
- 9026.0025 AK500415 (as printed)
- Measuring range
- 0 - 100 Pa differential (label)
- Analog output
- 4 - 20 mA (label)
- Accuracy
- +/- 1.0 % (label)
- Supply voltage
- 24 VDC (label), +20 % / -15 %
- Switch outputs
- 2 change-over relays, 230 VAC / 6 A resistive
- Measuring principle
- Inductive, beryllium bronze diaphragm
- Medium
- Air and non-aggressive gases
- Pressure connection
- 2 hose ports for 6.5 mm hose (+ and -)
- Housing
- Panel housing 48 x 96 mm (DIN 43700), cutout 92 x 45 mm
- Operating temperature
- +10 to +50 °C
- Electrical connection
- 12-pin terminal strip, 0.5 - 2 mm²
The Halstrup Walcher REG 21 is a panel-mount differential pressure controller that measures and displays low air pressure differences, outputs a proportional analog signal, and switches two relays at set points you program from the front keys. The unit in this listing is the 0-100 Pa version with a 4-20 mA output, 24 VDC supply and 2 relays, as printed on its type label. Because it has both a 4-20 mA output and switching relays, it is used as a differential pressure transmitter and as a pressure switch/controller at the same time, for example in clean rooms, ventilation and filter monitoring.
What does the type label say?
REG 21, 0 - 100 Pa, 4 - 20 mA, +/- 1,0 %, 24 VDC, 2 Relais, 9026.0025 AK500415, CE, Made in Germany. The front panel reads REG 21 with a red 4-digit LED display, the unit Pa, and the keys Set 1, Set 2, up and shift.
How does the REG 21 measure pressure?
According to the Halstrup Walcher manual, the pressure difference between the + and - ports moves a beryllium bronze diaphragm, and inductive pick-ups measure its deflection, so there are no wearing parts. The display, the analog output and the two switch outputs all follow that measurement. Connect the measured pressure to the + port and the reference pressure to the - port with 6.5 mm hoses.
How is it wired?
The connection label on the housing shows a 12-pin terminal strip: 1 Signal, 2 GND (analog output), 4-5-6 Relais 2, 7-8-9 Relais 1 (change-over contacts), 10 and 12 for the 24 VDC supply (- and +). The manual gives a relay rating of 230 VAC, 6 A resistive load, and a panel cutout of 92 x 45 mm.
What can be set from the front keys?
Time constant (1, 2, 5 or 10 s), display brightness, automatic or manual zero point calibration, and for each relay a switch-on value, switch-off value (hysteresis) and switch direction. The two relays can work as two separate limit switches or together as a three-point controller.
What is in the photos?
The REG 21 from the front, the top with the type label and wiring label, and the back with the + and - pressure ports and the green 12-pin terminal strip. Condition: used.
- Ships from
- Israel
- Tracking
- Included on every order
Import duties and taxes may apply in your country and are paid by the buyer on delivery.
- Returns
- Accepted within 60 days of delivery
- Return shipping
- Paid by the buyer
- Refund
- Money back
Return terms differ from item to item — this item's own policy is shown above.
Whatever it says, an item that arrives faulty or not as described is covered: tell us within 30 days of delivery and we will refund or replace it.
Consumers in the EU, the UK and Israel keep their legal right to cancel within 14 days. Full details and the return request form are on our Returns and warranty page.
Questions about this part
What is the Halstrup Walcher REG 21?
A panel-mount differential pressure controller with a digital display, an analog output and two relay outputs. This unit is the 0-100 Pa, 4-20 mA, 24 VDC version with 2 relays.
Is the REG 21 a pressure transmitter or a pressure controller?
Both. It sends a 4-20 mA signal proportional to the pressure like a transmitter, and it switches two relays at programmable limits like a pressure switch or controller.
What is the measuring range?
0 to 100 Pa differential, as printed on the type label.
What power supply does it need?
24 VDC, per the label. The manual gives a tolerance of +20 % / -15 % and a power input of 3 VA.
How do I connect the pressure hoses?
The measured pressure goes to the + port and the reference pressure to the - port, each with a 6.5 mm hose.
How do I zero a differential pressure controller like the REG 21?
The REG 21 has a manual zero point calibration from the front keys, and an automatic mode on units fitted with the internal short-circuit valve. The pressure must be zero during calibration.
What panel cutout does it need?
92 x 45 mm for the 48 x 96 mm panel housing, per the manual.
What condition is it in?
Used.
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