For a remote pump station, a signal repeater sits between a field transmitter (flow, level, pressure) and a controller or RTU, and the RFQ must lock the input signal type, output signal type, channel count, isolation, and hazardous-area class before the quote is meaningful. Yokogawa's field troubleshooting checklist lists supply voltage, polarity, pulse type (voltage/open-collector/non-voltage-contact/current pulse), and external resistor presence as the first items to confirm when a pulse repeater has no output [S1].
The same checklist, applied upstream as an RFQ spec, prevents that fault from ever being shipped: every parameter that can be wrong in the field must be pinned in the line item. Generic entries such as "signal repeater, 4-20 mA" force the vendor to assume, and the wrong assumption on a 4-wire vs 2-wire device or on HART pass-through costs the project a requote cycle plus field rework.
Input and Output Signal Type: the Decision That Drives Everything Else
The single most expensive mistake on a pump-station RFQ is leaving the I/O signal type as "analog" without specifying current vs voltage vs HART vs pulse vs digital [S1]. For 4-20 mA loops, the RFQ must state whether the repeater is 2-wire (loop-powered, 3.5 mA typical minimum operating current) or 4-wire (externally powered, signal isolated from power). Yokogawa's JUXTA M Series unified-signal converters, for example, are explicitly specified for 4-20 mA DC or 1-5 V DC I/O, which sets the range the vendor must support [S1].
For pulse signals, the RFQ must split into four sub-types, because each has different terminal hardware: voltage pulse, open collector, non-voltage contact, and current pulse. Open-collector and non-voltage-contact outputs require external power applied at the output terminals, and current-pulse inputs require an accessory resistor unless the model has built-in resistance, so any of these omissions sends the vendor back to engineering [S1].
Power, Isolation, and Channel Count for an Unmanned Pump Site
Remote pump stations typically run on 24 V DC battery-backed power with tolerances of 20-30 V DC, so the RFQ must state nominal voltage, tolerance, and the maximum inrush. Yokogawa's JUXTA F Series is documented at 24 V DC with DIN-rail, rack, or wall mounting, and the wider VJ Series accepts a wide-range power supply, two isolated outputs, and field-configurable models, a useful reference profile for the "wide-range supply, isolated output" line on a pump-station RFQ [S1].
Channel count is the second cost driver: a single-channel repeater for one flow signal costs a fraction of a 4-channel or 8-channel multi-loop unit, but the per-channel price of the multi-channel version drops sharply. For a typical pump station with flow, level, pressure, and a vibration probe, a 4-channel DIN-rail unit is the usual break-even point. Channel-to-channel isolation of 500 V AC or 1.5 kV AC must be specified if any input is athermocouple or a grounded RTD, otherwise ground loops show up as offset drift within weeks of commissioning.
Hazardous Area, IP Rating, and Temperature: Fields That Force a Requote if Blank
A pump station with a diesel-driven skimmer or a methanol dosing skid will sit in Zone 1 or Zone 2, and the RFQ must carry an ATEX 2014/34/EU category or an IECEx certificate number, not a vague "explosion-proof" note. For outdoor unmanned cabinets, IP66 is the typical minimum, with IP67 specified where the cabinet sits in a flood-prone sump. Operating temperature must be stated explicitly because commercial-grade isolators rated 0-50 °C will fail in a Texas summer pump skid, while industrial -40 to +85 °C units exist for the same DIN-rail footprint. [S1]
For sites with solar PV and a 12/24 V DC bus, the RFQ should add "loop-powered or 9-30 V DC" and reject anything that requires 110-240 V AC. Conductor cross-section matters because long cable runs at a remote pump station often mean 500 m to 1.5 km of shielded twisted pair, and the DC drop at 4-20 mA across that distance must be calculated against the repeater's minimum loop voltage; a 250 Ω HART resistor plus 1 km of 18 AWG can eat more of the loop budget than the transmitter itself.
Selection Criteria: How the Main Repeater Types Compare
For pump-station work, the four options a buyer will be offered are: passive loop-powered isolator, active 4-wire repeater, HART-multiplexer/repeater, and pulse repeater/rate converter. A passive isolator has no power connection and splits the 4-20 mA loop into two galvanically isolated segments, which fixes ground loops but cannot boost a fading signal at the end of a long cable. An active 4-wire repeater provides local power and signal regeneration, which is what most modern pump-station RFQs end up specifying because it also isolates and filters. [S1]
A HART-aware repeater passes the BELL 202 FSK layer in both directions and can multiplex multiple HART devices onto one multidrop line, which matters when a skid has six smart valves plus a flow meter. A pulse repeater or rate converter is a separate device family and Yokogawa explicitly differentiates it from the analog signal-conditioner line in the JUXTA family, with the same JUXTA M Series used for computing, peak-hold, and temperature/pressure compensation on the same DIN rail [S1]. On the four decision axes a buyer weights most (cost per channel, hazardous-area approval, HART transparency, and ability to drive a long cable), the active 4-wire HART-transparent repeater scores highest on three out of four and is the default pick for a new build.
What to Put on the RFQ Line, in Order, and What to Forbid
The line item, in the order a vendor will read it, should read: (1) function, e.g. "4-channel analog signal repeater, HART-transparent"; (2) input signal per channel, e.g. "4-20 mA, 2-wire or 4-wire, HART pass-through"; (3) output signal per channel, e.g. "4-20 mA, into 600 Ω max load"; (4) supply, e.g. "24 V DC nominal, 20-30 V DC"; (5) isolation, e.g. "1.5 kV AC channel-to-channel and channel-to-bus"; (6) hazardous-area approval, with the certificate number; (7) IP rating, e.g. "IP20 DIN-rail housing, install in IP66 cabinet"; (8) operating temperature, e.g. "-40 to +85 °C"; (9) cable distance, e.g. "designed to drive 1.0 km of 18 AWG shielded twisted pair"; (10) configuration port, e.g. "USB or HART modem for field setup". [S1]
What to forbid on the same line: "compatible with all PLCs" (no such device exists at the protocol layer), "wireless" (a separate RFQ family with a different EMI and battery budget), and "as per previous project" (forces the vendor to chase the old part number and re-quote from scratch). For projects that touch rotating equipment, a related reference on control-cabinet integration lays out the same discipline for the motor side; a similar pattern applies to signal repeaters, where the most expensive field failures are not the device but the missing parameter on the RFQ.
Common Failure Modes and How the Spec Prevents Them
The four field failures the Yokogawa checklist is built around are: no output at all (power, polarity, external resistor); output stuck at a fixed value (signal wiring or HART short); output saturated (over-range input or wrong span setting); and HART communicator cannot see the device (HART pass-through missing or termination resistor wrong) [S1]. Each one of these is traceable to a missing or wrong entry on the RFQ: missing supply tolerance leads to under-voltage lockout, missing polarity note leads to reversed wiring, missing "external resistor included" leads to a current-pulse input that never triggers, and missing "HART pass-through" leads to a vanilla isolator that filters the FSK layer.
For pulse channels specifically, the RFQ must add "input trigger level 5-24 V DC" for voltage-pulse inputs, "external pull-up 10 kΩ to 24 V DC" for open-collector outputs, and "current-pulse input with 100 Ω built-in shunt" or "external 100 Ω resistor supplied" for current pulses, all of which align with the JUXTA M Series and VJ Series plug-in signal-conditioner family that Yokogawa documents at the field-troubleshooting level [S1]. This is the level of detail that separates an RFQ that gets a clean quote in two days from one that bounces for three weeks.
Encyclopedia Anchors and Cross-Reference
For buyers who also need to specify a signal repeater alongside a remote I/O module on the same pump-station RTU panel, the same parameter list applies: I/O type, isolation, channel count, hazardous area, supply. Where a signal calibrator is used at commissioning, the calibrator must be able to source and read the same signal type the repeater is specced for, otherwise the loop test is meaningless. [S3]
Next node to track: when the vendor returns the quote, verify that the listed I/O type, isolation voltage, supply range, hazardous-area certificate number, and IP rating on the quote match the RFQ line item by item; a mismatch on any of these five fields is the single most common reason a pump-station signal repeater ends up back-ordered after the cabinet has been wired. The two trackable signals a buyer should watch on the resulting PO are the lead-time on the hazardous-area certificate (typically 4-8 weeks for IECEx) and whether the HART pass-through is firmware-version-locked to a specific host controller.