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PHTX-21/22/23:pH/ORP Preamplifiers

pH/ORP Preamplifiers

$79.00 PHTX-22

1 year warranty CE
  • Send pH Electrode Signal 0.3km (1,000') Over Ordinary, Wire and Connectors or Coaxial Cable.
  • Interface pH Electrodes Directly with Inexpensive mV Meters and Recorders or Sophisticated Process Controllers and Data Acquisition Systems.
  • Extend Useful Life of pH Electrodes.
  • Available With/Without Automatic Temperature Compensation.
Industrial pH Instrumentation and Electrodes - View related products


OMEGA’s PHTX-20 series Preamps are unity gain preamplifiers which convert the high impedance mV signal of a pH or ORP electrode to a low impedance signal. This signal can travel up to 1,000 feet using ordinary wire and connectors to high impedance input pH meters and controllers (such as OMEGA’s PHCN-37 vol. 29 pH and Conductivity Handbook, page 84), and to standard Process Meters and Controllers such as the DPi/CNi which could not otherwise interface with the high impedance signal. In many applications the PHTX-20 series Preamps will be able to extend the useful life of expensive pH electrodes. By lowering the output impedance of ageing electrodes, the PHTX20 allows them to continue to function and provide a measurable signal.

The PHTX-21 is powered by lithium batteries with an estimated life of 5 years when used with high input impedance instruments. The electronics are entirely encapsulated in an epoxy filled stainless steel enclosure. The input and output connections are industry standard BNC. The output can be split from coaxial to separated leads with the 3073 adapter.

The PHTX-22 is a 10-40 volt dc powered preamp. Power can be provided by the excitation of a process meter (such as the DPi8) or the optional power supply. The electrodes are entirely encapsulated in a compact epoxy filled enclosure designed for easy mounting in a manufacturing process. The PHTX-22 offers redundant outputs from either a BNC connection, terminal strip or both at the same time.

The PHTX-23-ATC is the same as the PHTX-22 (above) with the added feature of Automatic Temperature Compensation. With the output of a PHTX-23-ATC automatically compensated for temperature variations, it is possible to use an inexpensive but sophisticated process meter or controller such as the DPi/CNi series to monitor and control pH in place of more expensive dedicated pH units. The Automatic Temperature Compensating element required is a 1,000 Ohm RTD. (ATC is not used on ORP measurements.)

Common Specifications
Output Offset: 1 mV typical; 2 mV max. which corresponds to 0.033 pH
Input Impedance: 10 to the 13 Ohms
Output Impedance: 20K Ohms
Output Voltage: -2000 mV to +2000 mV
Operating Temperature: 0 to 60°C (32 to 140°F)
PHTX-21 Internal Battery Powered Model
Dimensions: 95.25 L x 17.8 mm D (3.75" x 0.7")
Weight: 5.7 g (2 oz.)
Battery Life: Approximately 5 Years
PHTX-22, PHTX-23-ATC External Powered Dual Output Model
Power: 10 to 40 Vdc
Dimensions: 38.1 H x 76.2 W x 38.1 mm D (1.5 x 3 x 1.5")
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What Other People Bought: When you see this icon, click on it to expand a list of products that other people have bought when they purchased this model.

Part Number/Desc.
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pH Preamplifier, single output, battery powered
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pH Preamp, 10 to 40 Vdc powered
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pH Preamp, 10 to 40 Vdc, Auto Temp Comp
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BNC to Banana Plug adapter
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4.01 pH buffer solution 475 ml bottle
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7.01 pH buffer solution 475 ml bottle
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Regulated power supply, 24 Vdc, 400 mA, UL, 1.8 m (6') cord with stripped leads
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Regulated power supply, 12 Vdc, 1.2 A, with stripped leads
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Strain/process meter
All amounts shown in USD
Note: Each unit supplied with operator’s manual.
Ordering Example: (1) PHTX-21 pH preamplifier, $69.00   plus (1) PHEH-65-10 Mounting assembly for PHE-6510, $72.00  plus (1) PHA-4  4.01 pH buffer solution 475 ml bottle, $10.00  plus (1) PHA-7  7.01 pH buffer solution 475 ml bottle, $10.00, $69.00 + 72.00 + 10.00 + 10.00 = $161.00