Dwyer APM/MPM/PPM sensor

Register map(s) for this device, with a note of how far each has been checked. Addresses are 0-based, as on the wire. Scale and byte order are confirmed only at the hardware-verified rung.

coherence-checked

Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.

point	address (0-based)	type	scale	unit
pv_rate_display_value	0	F32BE	1	User defined
alarm_and_relay_status	2	U16	1	None
digital_inputs_and_outputs_status	3	U16	1	None
maximum_display_value	4	F32BE	1
minimum_display_value	6	F32BE	1
total_value	8	F32BE	1
grand_total_value	10	F32BE	1
total_overflow_value	12	F32BE	1
total_non_overflow_value	14	F32BE	1
grand_total_overflow_value	16	F32BE	1
grand_total_non_overflow_value	18	F32BE	1
pv_rate_display_value_long	20	U32BE	1
maximum_display_value_long	24	U32BE	1
minimum_display_value_long	26	U32BE	1
total_value_long	28	U32BE	1
grand_total_value_long	30	U32BE	1
total_overflow_value_int	32	I16	1
total_non_overflow_value_long	33	U32BE	1
grand_total_overflow_value_int	35	I16	1
grand_total_non_overflow_value_long	36	U32BE	1
pv2_display_value	182	F32BE	1
pv2_display_value_long	184	U32BE	1
pv1_percent_display_value	186	I16	1
analog_output_value	400	U16	1	uA

link settings as documented (unverified): RTU; default 2400 8E?; unit ID 247; FC 03,04,06,16; All 4x Registers are mirrored into 3x register space, and are therefore capable of being read by Modbus function 04 (Read Input Registers).

⚠ As is typical with most instruments, the addition of serial communications carries an inherent risk; it allows a remote operator to change the operation and/or characteristics of the device being digitally communicated with. Inappropriate communication could have serious consequences in meter or system operation. — Starkest reads only; we never write a control register.

bench facts as documented (unverified)

protocol notes	Writing a value that is outside the parameters range will force it to be limited to the closest value within the range.
model register	49901
firmware register	49905
identification notes	Product Identifier is at 49901-49904, Firmware Version is at 49905-49908.
doc revision	LIMModbus2DW_A.doc 10/10

field reports — community-sourced, unverified (checked 2026-06-11)

confirmed: Baud rates (300-19200), default baud (2400), default Unit ID (247), and Even parity — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables
confirmed: All 4x registers mirrored into 3x space for Function 04 reading — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables
confirmed: Control warning text — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables, Page 2
confirmed: Identification registers (Model at 49901, Firmware at 49905) — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables, Table 6
confirmed: Out-of-range writes limited to closest boundary — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables, Note 4
confirmed: Register map addresses (0-based 0, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 182, 184, 186, 400) — confirmed by Dwyer APM/MPM/PPM Modbus Register Tables

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

generated — A prompt produced it. Unproven — anyone can regenerate this.
structure-verified — Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.
coherence-checked — Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.
hardware-verified (software-key) x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

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