A Rosemount 3051 model number looks like a serial number and behaves like a sentence. Every character is a choice somebody made, and the ordering matrix in the product data sheet is the grammar that governs it. Read it left to right and the string tells you the measurement type, the pressure range, the output protocol, what the wetted parts are made of, what the housing is, and which options were bolted on. Read it wrong and you have ordered an absolute transmitter for a differential job.
This guide walks that grammar for the two platforms the Rosemount 3051 Model Number Builder covers: the 3051C coplanar platform, which gives you the 3051CD differential, 3051CG gage, and 3051CA absolute variants from one matrix, and the 3051SAL scalable level platform, where the diaphragm seal system is carried inside the same model number. It is written against Emerson product data sheet 00813-0100-4001 Rev WG (October 2025) for the 3051C and 00813-0100-4801 Rev UW (April 2026) for the 3051SAL, which are the revisions the builder data was audited from.
1. The Anatomy of a 3051 Model String
A 3051C model string is a family prefix, then one character per required position, then option codes appended on the end. Take the standard differential configuration:
3051CD2A22A1A/M5
The same string is written without the separator on distributor listings as 3051CD2A22A1AM5. Both forms decode to identical segments, so do not read a missing slash as a different product. Broken out:
| Segment | Position | Meaning | PDS page |
|---|---|---|---|
| 3051C | Family prefix | Coplanar platform | 7 |
| D | 1. Measurement type | Differential, so the instrument is a 3051CD | 8 |
| 2 | 2. Pressure range | Range 2. On a differential unit that is minus 250 to plus 250 inH2O | 8 |
| A | 3. Transmitter output | 4-20 mA with a digital signal based on HART protocol | 9 |
| 2 | 4. Materials of construction | Coplanar SST flange with SST drain and vent | 9 |
| 2 | 5. Isolating diaphragm | 316L SST, NACE MR0175 compliant | 9 |
| A | 6. O-ring | Glass-filled PTFE | 9 |
| 1 | 7. Sensor fill fluid | Silicone | 10 |
| A | 8. Housing material | Aluminium with a 1/2-14 NPT conduit entry | 10 |
| M5 | Option | LCD display | 15 |
Every one of those is an option the data sheet flags as common, which is why it is the worked example in the builder. Eight required positions, then as many option codes as the configuration needs. The 3051SAL runs the same idea over eleven required positions plus a seal style position that opens a branch, because a level transmitter with a seal system has a lot more geometry to describe.
2. The Range Code Is a Pointer, Not a Pressure
This is the trap worth learning first, because it is silent. The pressure range digit does not carry a pressure. It selects a row in a table whose column is chosen by the measurement type at position 1.
On the 3051C, Range 2 on a differential (D) or gage (G) unit is minus 250 to plus 250 inH2O. The same Range 2 digit on an absolute (A) unit is 0 to 150 psia. Range 1 behaves the same way: minus 25 to plus 25 inH2O on D and G, 0 to 30 psia on A. Range 0 exists only on differential and carries a footnote of its own, because a 3051CD0 is available only with HART or wireless output and only with a restricted set of flange, diaphragm, o-ring, and bolting combinations.
So changing D to A on a finished string is not a variant swap. It changes what the instrument measures and it changes the pressure it measures. The builder re-resolves every context-dependent meaning against the current path rather than caching the first one it displayed, and where the source table gives no meaning for a code on the path you are on, it withholds the code and blocks assembly rather than showing a plausible range.
The 3051SAL has the same structure with a different trigger: there the range column is chosen by the pressure module type at position 3, which is D for a coplanar differential sensor, G for a coplanar gauge sensor, or T for an in-line gauge sensor.
3. What Each 3051C Position Controls
Eight required positions, and each one closes off a different kind of question.
| Position | What it decides | Common (starred) choices in the data sheet |
|---|---|---|
| 1. Measurement type | Differential, gage, or absolute. Also selects the range column. | D differential, G gage. A absolute is tabulated but not starred, and with wireless output it is restricted to a 316L SST diaphragm and silicone fill. |
| 2. Pressure range | The span the sensor is built for, read against the measurement type. | Ranges 1 through 5 on D and G. Range 0 is differential only and carries its own restriction footnote. |
| 3. Transmitter output | How the signal leaves the instrument, and it gates a lot of what follows. | A HART 4-20 mA, F FOUNDATION Fieldbus, W PROFIBUS PA, X WirelessHART. M low power 1-5 Vdc HART is tabulated but restricted to a named list of certifications. |
| 4. Materials of construction | The transmitter flange and the drain and vent material. | 2 coplanar SST with SST drain and vent, 3 cast C-276, 4 alloy 400, 5 plated carbon steel, 7 SST flange with C-276 drain and vent, 8 plated carbon steel with C-276, 0 alternate process connection for use with an alternate or level flange option. |
| 5. Isolating diaphragm | The wetted diaphragm, which is the part the process actually touches. | 2 316L SST and 3 alloy C-276 are both NACE MR0175 compliant. Alloy 400, tantalum, gold-plated alloy 400, and gold-plated 316 SST are tabulated but not starred, and none of them are available with wireless output. |
| 6. O-ring | The seal between the flange and the sensor module. | A glass-filled PTFE, B graphite-filled PTFE. The gold-plated alloy 400 diaphragm requires the B o-ring. |
| 7. Sensor fill fluid | The fluid behind the diaphragm that transmits pressure to the sensor. | 1 silicone, 2 inert (differential and gage only, and not with wireless output). |
| 8. Housing material | The electronics enclosure and the conduit entry thread. | A aluminium with 1/2-14 NPT, B aluminium with M20, J SST with 1/2-14 NPT, K SST with M20. Engineered polymer P exists only with wireless output; the G1/2 variants exist only with the I1 certification. |
Notice how far position 3 reaches. The output protocol gates housing choices, wireless option codes, several certifications, and a list of diagnostic and display options. That is why it sits early in the sequence, and why changing it late in a configuration usually invalidates something downstream.
4. The 3051SAL Level Platform: Eleven Positions and a Branch
The 3051SAL puts the diaphragm seal system inside a single model number instead of pairing a transmitter model with a separate seal model, which is the whole point of the platform. That costs more positions.
| Position | What it decides |
|---|---|
| 1. Performance class | Code 1 Ultra at 0.055 percent of span with 150:1 rangedown and a 15-year limited warranty, or code 2 Classic at 0.065 percent of span with 150:1 rangedown. |
| 2. Configuration type | Fixed at C, liquid level transmitter. |
| 3. Pressure module type | D coplanar differential, G coplanar gauge, or T in-line gauge. This selects the range column. |
| 4. Pressure range | A two-character code read against the pressure module type. |
| 5. Transmitter output | A HART 4-20 mA, F FOUNDATION Fieldbus (which requires a Plantweb housing), or X WirelessHART (which requires a wireless Plantweb housing and an intrinsically safe approval code). |
| 6. Housing style | A two-character code: Plantweb housing in aluminium or SST with NPT, M20, or G1/2 entry; wireless Plantweb; or a junction box housing with output for a remote display and interface. |
| 7. Seal system type | Read against the pressure module type at position 3. |
| 8. High side connection | The process connection on the high side of the seal system. |
| 9. Low side connection or capillary inner dimension | Either the low side process connection or the capillary bore, depending on the seal system. |
| 10. Capillary length | The run length between the seal and the transmitter. |
| 11. Seal fill fluid | The fill in the seal system, which sets the temperature limits of the installation. |
| 12. Seal style | Opens one of nine branches (FF, EF, RF, PF, FC, RC, RT, SC, SS), each carrying its own positions from there. |
The seal style branch is the structural difference from the 3051C. Picking a branch does not just append a code, it changes which positions exist after it. That is also why the 3051SAL matrix runs from page 101 to page 135 of its data sheet while the 3051C matrix fits in pages 7 to 18.
5. Starred Standard Options and the Ones That Set Your Lead Time
Emerson stars the options it considers common. That star is a sourcing signal, not a technical recommendation. A starred option is one that is normally built without a special routing; a non-starred one is a segment somebody has to look at before the order can be scheduled, and that is where lead time comes from.
The option table is large. The 3051C carries 122 option codes across 42 categories, and the 3051SAL carries 156 across 43. The categories are practical rather than abstract: approvals, mounting brackets, alternate and level flanges, bolting, displays, configuration buttons, diagnostics, calibration and material certificates, alarm levels, cleaning, conduit connectors and plugs, transient protection, shipboard approvals, cold temperature operation, static pressure, seal assemblies, and warranty.
A handful come up constantly and are worth knowing by sight:
- M5 LCD display, M4 LCD with local operator interface, M6 graphical LCD (HART 4-20 mA only).
- Q4 calibration certificate, Q8 material traceability per EN 10204 3.1, Q15 certificate of compliance to NACE MR0175 and ISO 15156 for wetted materials.
- QT safety certified to IEC 61508 with an FMEDA certificate, HART 4-20 mA only, and T9 enhanced SIS proof testing and logging on the same restriction.
- DA1 loop integrity and plugged impulse line diagnostics.
- K5 USA explosion-proof, dust ignition-proof, intrinsically safe, Division 2 (FM); I1 ATEX intrinsic safety; E8 ATEX flameproof.
- B4 coplanar flange bracket, all SST, for 2 inch pipe and panel; L4 austenitic 316 SST bolts.
- S1 assemble to one Rosemount seal, which is how a coplanar transmitter gets married to a 1199 or 1299 seal that still has its own model string.
- P9 4500 psig static pressure limit, on 3051CD ranges 2 through 5 only.
- BR5 cold temperature operation to minus 58 F (minus 50 C), restricted to silicone fill, a 316 SST or compatible diaphragm, and flange types 2, 7, or 0.
Several of those carry a requires or not-available-with condition, which is the point: an option table is not a menu, it is a constraint system. The builder evaluates those conditions against the path you are on and lists the reason when a code is refused.
6. The Restrictions Nobody Checks
Most compatibility rules in the ordering table are broken out into codes, and anything broken out into codes can be checked mechanically. Some are not. They exist as a sentence in the middle of an option row, and a sentence cannot be evaluated without guessing what it means.
Two examples from the 3051C table. The drinking water approval option lists a long set of things it is not available with, running from alloy C-276 and tantalum isolators through cast C-276 and plated carbon steel flanges, DIN and level flanges, manifolds, seals, primary elements, surface finish certification, and the remote seal report. The Japan flameproof approval is restricted to HART, FOUNDATION Fieldbus, or PROFIBUS PA output, and to an aluminium housing with a 1/2 NPT entry only.
The builder collects every restriction of that shape into a caution card headed "Restrictions this tool could not check", with the segment, the code, and the page number, and it says plainly that it did not evaluate them. That is a deliberate choice. An automated check that quietly mis-parses a sentence is worse than no check, because it produces confidence instead of a second read. Read that card against the order before it goes out; it is short, and it is where the surprises live.
7. Four Common Configurations, Read Segment by Segment
These are shapes rather than recommendations. Each one is the set of ordering constraints that follow from one decision, taken from the same tables.
1. Standard differential HART loop. 3051CD2A22A1A with M5. Differential, Range 2, HART 4-20 mA, coplanar SST flange with SST drain and vent, 316L SST diaphragm, glass-filled PTFE o-ring, silicone fill, aluminium housing with 1/2-14 NPT, LCD display. Every segment is a starred common option, which is why this configuration quotes quickly. Add K5, I1, or E8 for the area classification you are installing into and Q4 if the job needs a calibration certificate.
2. Gage instead of differential. Change position 1 from D to G and read the range again, because the range column changes with it. Nothing else in the standard string is forced to move, which is what makes CD and CG feel interchangeable and why the range check gets skipped. Do the range check.
3. Wireless. Output X pulls a chain of consequences: it requires the engineered polymer housing (P) and it is restricted to intrinsically safe approvals only. It also rules out a long list of options that are perfectly normal on a wired unit, including the inert fill fluid, the alloy 400, tantalum, and gold-plated diaphragms, the transient protection terminal block, the external ground screw, the conduit plug and connector options, and the ABS and DNV shipboard approvals. If the wireless decision is late, expect to rework the string.
4. Safety-instrumented loop. QT (safety certified to IEC 61508 with an FMEDA certificate) and T9 (enhanced SIS proof testing and logging) are both HART 4-20 mA only, so output A is not a preference here, it is a prerequisite. That constraint runs the same direction as the graphical display M6 and the analog zero and span buttons, all of which are HART-only as well.
8. Handing the Code to a Distributor
Rosemount does not sell through one national storefront. Emerson routes through local business partners assigned by territory, and the public path past common options is a lead form rather than a store. That means the model string is the beginning of a conversation, not the end of one, and the quality of that conversation depends on what you send.
What an inside sales desk needs, in one message: the manufacturer, the platform, the full model number, the source revision you built it against, the specification broken out segment by segment with standard and special marked, the quantity, the need-by date, the tag number, and any application note that explains an unusual segment. The builder assembles exactly that block, laid out the way an Emerson configuration data sheet is laid out, so it can be pasted into an email without translation. It copies to the clipboard or opens a mail draft with an empty recipient line that you address yourself; nothing is sent anywhere and no email address is collected.
Two things to say out loud in that email. First, name the revision you built against, because page citations point at a specific product data sheet revision and a newer one can add, move, or withdraw a code. Second, flag the special segments yourself rather than waiting to be asked, because those are the ones that determine whether the quote comes back in two days or three weeks.
And keep the boundary clear in your own head: a model number is not a quote and it is not a certificate. Availability, price, lead time, and regional option support are not in the data sheet at all, and a hazardous-area approval code on an order is not the same thing as a certificate accepted by your authority having jurisdiction.